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Quantitative > Lets have it lad > Flashcards

Lets have it lad Flashcards

1
Q

Add together

A

=sum

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2
Q

what symbol in edit bar means auto sum

A

Ʃ

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3
Q

Multiply

A

*

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4
Q

Divide

A

/

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5
Q

Subtract

A

-

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6
Q

Mean

A

=Average()

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7
Q

Median for even numbers

A

Middle two, add together divide by two

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8
Q

Median

A

Sort and filter icon, smallest to largest to put them in order

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9
Q

Mode

A

=mode()

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10
Q

Range

A

=Max() and =min()

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11
Q

Interquatile range

A

Put in numeric order
Split into 4 quarters
Subtract first value of 2nd quarter from last value of 3rd

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12
Q

Standard deviation

A

=STDEV()

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13
Q

Variance tpye

A

=VAR()

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14
Q

What is variance

A

STDEv without square root

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15
Q

How do you calculate stdev

A

Calculate mean, x with line above means mean
Difference of each x value and mean then square
Take sum of all square
Then divide by number of parts minus 1
Square root

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16
Q

Square data

A

data^2

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17
Q

What are the two types of statistical analysis

A

Descriptive stats

Inferential stats

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18
Q

What is descriptive stats?

A

Statistical analysis to summarise main points/characteristics of data

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19
Q

What is inferential stats

A

Statistical analysis to infer something about a whole form sample

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20
Q

Nominal data

A

PLace in categroies, labelled- options

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21
Q

Ordinal data

A

Preferences shown and then presences ranked, scale 1-5

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22
Q

Interval data

A

Any values that have a consistent interval, how hot

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23
Q

Ratio

A

Has a defined 0 point, distance travelled

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24
Q

What is the mean very sensitive to?

A

extreme values

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25
Q

What is the median compared to the mean?

A

Much less sensitive, more robust

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26
Q

For nominal data what should be used, descriptive stats

A

Mode

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27
Q

What should you use for quantitative data?

A

Mean or median

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28
Q

When should you use median over mode

A

When. there are extreme values because you do not want a distorted average

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29
Q

When should you use mean over median

A

When there are no extreme values

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30
Q

What are the 4 measures of spread

A

Range
Standard dev - most common
Interquartile range
Variance

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31
Q

What is the standard deviation used for?

A

Measure the variability in data

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32
Q

What does a high standard dev mean?

A

high change

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33
Q

wHat does a low standard dev mean>

A

low change

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34
Q

Example of standard dev?

A

LAI values of rainfall

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35
Q

What is variance

A

Calculates variation which is not in the same units as the data (squared units)- less common

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36
Q

What are histograms?

A

Graphic depiction of the shape of the distribution of data- most common

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37
Q

What is the issue w to many intervals in a histogram?

A

Too complex

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38
Q

What is the issue with too few intervals in a histogram?

A

Detail is lost

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39
Q

What is the ideal number of intervals in a histogram?

A

Ideal=10 to 20

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40
Q

4 measures to describe the similaries/differences of frequency distributions

A

Central tendency
Spread
Skewness
Kurtosis

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41
Q

Skewness

A

Measure of asymmetry in distribution

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42
Q

Skewness, low numbers

A

Positively skewed distribution

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43
Q

Skewness High numbers

A

Negatively skewed distribution

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44
Q

No skew

A

0

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45
Q

Sew =

A

Mean-median

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46
Q

+ve value skew

A

+ve skew

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47
Q

-ve value skew

A
  • e skew
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48
Q

Kurtosis

A

Measure of how flat or peaked a distribution is

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49
Q

Kurtosis, Platykurtic

A

Relatively flat distribution w no obvious peak

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50
Q

Kurtosis, Leptokurtic

A

strongly pronounced peak in data

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51
Q

Culmative frequency graphs, steep slope

A

Intervals with many data points

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52
Q

Culmative frequency graphs, shallow slope

A

intervals with few data points

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53
Q

What are calmative frequency graphs used for )example)

A

grain size statistics

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54
Q

What is used to raph 2 variables

A

Scatter plots

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55
Q

Nominal data os

A

-Categroical data

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56
Q

What is nominal data frequnctly expressed as?

A

Pie charts, good at showing proportion

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57
Q

Cna histograms still be used for nominal data?

A

-Yes, intervals=categories and frequencies = number of x in each category

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58
Q

How is nominal data expressed?

A

Histograms and pie charts

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59
Q

What do frequency distribution histograms show?

A

Visually describe distribution and indetify skewness and kurtosis

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60
Q

How do you decide size of intervals on histogram

A

Total (highest value) divided by the number of intervals you want

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61
Q

How do you calculate the number of individuals in each class interval

A 
=fequencey(data cells, class interval cells)
highlight range of cells to put the answer into first
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62
Q

How do you produce freuencey distribution histogram?

A

insert tab-charts-coumn

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63
Q

Skew function

A

=skew()

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64
Q

What is a normal skew distribution?

A

0

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65
Q

Why are sampling and inferential stats important

A
  • Rare to be able to sample a whole population

- Use characteristics of sample t infer

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66
Q

What is random sampling

A

Selecting individuals with no bias

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67
Q

What is systematic smapling

A

Individuals selected in a regular way

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68
Q

What is spatial sampling

A

individuals are selected at regular spatial intervals

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69
Q

Criteria for truly random samples

A
  • Every individual has an equal chance of inclusion throughout the procedure
  • Selection of any individual should not affect the chance of selection for another
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70
Q

Positive/negatives of systematic sampling

A

+allows fair/even coverage of range of individuals

-Not fair and equal chance of being chosen, can produce bunching of sampled individuals

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71
Q

Two key assumptions which underpin most inferential stats

A
  • random sampling

- population has a known distribution

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72
Q

What is a parameter

A

number that describes data from a population

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73
Q

What is a statsistic

A

A number that describes data from a sample

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74
Q

How to use random generator on excel

A

=RaNDBETWEEN(1,200), pulldown for cells below, rapsate answers and click paste special

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75
Q

Where to find look up feature

A

Lecture week 4

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76
Q

What is a hypothesis?

A

Proposed explanation for narrow phenomena, based on a range of things e.g. background scientific knowledge, preliminary investigators, logic, etc.

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77
Q

What is a theory

A

structure conceived by human imagination to explain how/why patterns occur in observed data

  • often broader and can integrate many hypotheses
  • new oe very well tested
  • can be used to generate hypotheses
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78
Q

What must hypotheses be to be a science?

A

testable

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79
Q

Why can descriptive statistics be used to make hypotheses?

A

We can make hypotheses based on observed patterns

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80
Q

Hypotheses can be formalised for what?

A

statisical testing

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81
Q

Null hypotheses, symbol

A

H0

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82
Q

What is a null hypothesis

A

accepted fact which is nullify able/invalidatable

83
Q

Research hypotheses

A

H1, what we want to find the answer to

84
Q

What is a 2 tailored test

A

Test to look into difference of means , could be 2 stats

85
Q

what is a 1 tailored test

A

Only one way it could happen

86
Q

What happens if there is evidence of statically significantly different between sample and overall mean?

A

We reject null and accept h1

87
Q

What happens when we cannot reject null

A

If null hypohtesis cannot be statically evidence against, then it has to be accepted

88
Q

What does an alternative hypothesis do?

A

Reject null

89
Q

What is the only purpose of inferential stats?

A

Answer the quesiton

90
Q

What is simulation modelling?

A

Testing all outcomes that might occur due to random variation and sampling- it is very slow and inelegant for well known process, but hd to do it top prove a point

91
Q

Null hypotheses is what we?

A

test to reject, from which we may accept

92
Q

What must we do to apply statistical tests?

A

We need to generate full hypotheses

93
Q

What do inferential stats allow us to do?

A

Use sample statistics to comment on a populations paramters

94
Q

Mode function

A

=Mode()

95
Q

Function for m, slope

A

=slope()

96
Q

Function for y intercept of line, c

A

=intercept()

97
Q

Function for correlation between populations, r, Pearsons

A

=pearson()

98
Q

r, correlation function

A

=correl()

99
Q

Variance function

A

=VAR

100
Q

What are sample figures called? (mean, mode and median)

A

Statistics

101
Q

What are the true mean and median of a population called?

A

Parameters

102
Q

What is used to estimate a parameter?

A

Statistics

103
Q

What do statistics describe?

A

Sample

104
Q

What do parameters describede?

A

population

105
Q

How likely is it that a sample will give exact estimates of the population characteristics?

A

unlikely

106
Q

What are different samples of the same population likely to compare?

A

Unlikely to have the same estimates of the population

107
Q

What is sampling distribution?

A

Distribution of a large number of sample statistics

108
Q

What is confidence interval?

A

Used to assess the accuracy of parameter estimates… and this is what allows us to test hypotheses

109
Q

What is standard error?

A

Standard deviation/square root of sample size

110
Q

Confidence interval

A

mean of x, plus or minus the standard error over the route of the sample size, times by the chosen Z value

111
Q

What is standard deviation of the means called?

A

Standard error

112
Q

What does standard deviation quantify?

A

The variation within a set of measurements

113
Q

What does standard error quantify?

A

the variation in the means of multiple measurements, can still do form single measurements

114
Q

Why statistical tests are needed?

A

Sample data, each mean value is to the same degree in error (it differs from the actual or population mean value of that site

115
Q

Why can difference in mean values from same population occur?

A

Sampling chance

116
Q

What is statistical significance?

A

level of risk ( a value); the risk of not being correct if we accept or reject null hypothesis

117
Q

What does a lowering statistical significance mean?

A

Higher confidence

118
Q

What do parametric statistical tests involve?

A

Assumptions of populations

-Populations should have some variance, independent date and hypothesis usually concern population ean

119
Q

What are non parametric test in comparison?

A

-Have fewer assumptions and are more robust, handle non classical distributions e.g. chi squared

120
Q

What stats test to use for nominal data?

A

test for promotion, difference of two proportions, chi squared independence

121
Q

What stats test to use for interval ratio?

A

Most commonly mean, difference of two means and regression analysis

122
Q

What is ordinal data?

A

Between both nominal and interval data

123
Q

If there is one sample…

A

test for proportion and test for mean

124
Q

If there is two samples..

A

Difference of two proportions and difference of two means

125
Q

What test if there is one sample with two measures?

A

chi squared , regression and difference of two emasn

126
Q

What if you are testing for a value?

A

test for proportion, test for mean and difference of two means

127
Q

What if you are comparing 2 statistics?

A

Difference of tow proportions/means

128
Q

Working out a relationship?

A

Chi squared, regression analysis

129
Q

What is the T - Test for?

A

Individual sampels

130
Q

What does t mean?

A

Difference between means/standard error of that difference

131
Q

What is critical value calculated based on?

A

Degrees of freedom and significance level

132
Q

What is the rejection reigon?

A

Part of the probability distribution beyond the a critical value of test statistic

133
Q

What is regression?

A

Nature of relationship between two variables

134
Q

What is measured by a correlation coefficient?

A

An association between two variables

  • poistive or negative
  • linear or non-linear
  • visualization or scatter plot
135
Q

Positive correlation

A

/

136
Q

Negative correlation

A

\

137
Q

Linear correlation

A

Close together and ordered

138
Q

+1 correlation

A

Perfect correlation

139
Q

0 correlation

A

no association

140
Q

-1 correlation

A

Perfect negative association

141
Q

0.00-0.19 correlation

A

very weak

142
Q

0.2-0.39 corerlation

A

weak

143
Q

0.4-0.69 correlation

A

modest

144
Q

0.7-0.89

A

strong

145
Q

0.9-1.0

A

very strong

146
Q

What are the different estimates of correlation coefficient?

A

Parametric and no para metric

147
Q

what is the parametric correlation estimate?

A

Pearsons product, moment correlation coefficient - asses normal distribution needs values

148
Q

What is the non-parametric correlation estimate?

A

Spearmans rank korrelation coeffiencent- more effective, only needs rank

149
Q

Pearsons rank

A

_requires interval scale (continuous data)
-Parametric assumes variables are normally distributed
Relationship between two variables tested is linear
-Should be in a consistent idrection

150
Q

Spearmans Rank

A

Ordinal or interval dara
Assumes direction of relationship consistent
only 91% of power?

151
Q

Spearmans rank equation

A

Look online

152
Q

Pearsons rank equation

A

Look online

153
Q

Steps of a stats test

A

-1 A Statement of the null hypothesis
Set the level of risk, statistical significance (Alpha value)
Select the appropriate statistical test and compute the test statistic value
Find critical value from published tables
Accept or reject hypothesis

154
Q

What is a correlation coefficient?

A

Numerical index that reflects the linear relationship between two variables, which ranges from -1 to 1

155
Q

Two types of correlation coefficient used

A

Spearmans rank and Pearsons

156
Q

How can the significance of Roy and rs be tested?

A

Using the T test

157
Q

How do you produce a scatter plot

A

highlight data, inset select x-y scatter chat type with only dots. Right click to alter, select chart layout tab to do the

158
Q

What should be done for sample data to get an unbiased estimation of rs values?

A

Coefficient should be multiplied by n-1/m

159
Q

How do you work out spearman’s rank

A

find difference between each pair of ranks, copy formula down column

  • sqaure the rank difference, pull down column
  • Add squared diffrences
  • Tied dat= complex
  • Non tied data = simple
160
Q

How do you work out spearman’s rank using a scatter graph

A

scatter graph, add trend line, chart elements-add. Double click trend line and click show more. Square root r2 (squared) value for (Coefficient of determination) Pearsons

161
Q

How to test significance for correlation data

A

put r value into T=r route over brackets with n-2 over 1-r squared inside

162
Q

Regression

A

A parametric stats technique for identifying the relationship between dependant variable and one or more independent variables

163
Q

What does a correlation tell us?

A

If 2 variables vary together

164
Q

What does a regression describe

A

Functional relationship between 2 variables

165
Q

What is the regression coefficient?

A 
y=a+bx
y=dependant variable
a=intercept on y axis
b= slope gradient
x=independant variable
166
Q

What does the regression coefficient show?

A

Provides diagnostic details that indicate the quality of the model fit
-used to provide a simplified relation between the two variables to evaluate the strength of the relation and correlation of the model based on sample data

167
Q

Dependant variable

A

Depend on the values of other variables

168
Q

Best fit line+

A

Sum of the square residuals minimised- determine b (slope) and a intercept for best fit line

169
Q

Slope = b , equation

A

Sum of (x-(mean X) X (y-(mean y) over Sum of x-(mean X) squared

170
Q

What is the coefficient of determination?

A

r2 (squared) between 0 and 1.0

- What proportion of total variance in the dependant variable is accoiunted for by the regression model, squared peasn

171
Q

What do higher rates of the coefficient determination mean?

A

Less scatter along the line

172
Q

What must be apparent for a relation to exist in the coefficient determination?

A

b must be different from 0 for a relation to exist

173
Q

What is the T test used for with regardless to the slope?

A

See whether it is significant or not

T test can be used for both slope (b) and interecpet

174
Q

If there is no relationship between X and Y what would the coefficient be expected to be?

A

0

175
Q

How can you also test the slope?

A

Convert calculated value for b into units of T to to compare T statistic with T critical value- the larger the T value the less likely that the slope coefficient for the sample arose from random sampling of variables that are not related

176
Q

Standard error of the estimate

A

Measures the amount of variability in the points around the regression

177
Q

Limitations of linear regression?

A

-Interval scale (continuous data) required
Data should be approx. normally distributed
-Equation should not be used to predict values for beyond limits of original data
-Relationship assumed linear shears non linear fit may provide better fit to same data sets.
-Residuals of regression should be approx normally distributed with a mean of 0.
Variance of y about regression line does not vary markedly over range of x

178
Q

How do you add linear regression line to the plot?

A

left click on data series to select- layout out tab, analysis group and click on add trend line- more trend line options and linear regression, check boxes to display the lines equation and r squared

179
Q

What is the slope function to obtain b data ?

A

=Slope (Known y’s, known x’s)

180
Q

What is the function to obtain intercept data, a?

A

=intercpet (known ys, known XS)

181
Q

Pearsons function

A

=Pearson()

182
Q

How do you calculate regression using the tool?

A

Select regression from data analysis tool data tab- data analysis group, if not options file- options add in

183
Q

what test for slope coefficient hypothesis?

A

T test

184
Q

The larger the value of t…

A

the less likely that the slope coefficient for the sample arose from random sampling of variables that are not linearly related

185
Q

What is confidence interval related to?

A

Standard error of the estimates

186
Q

What is the standard error of the estimates S.E

A

Average amount of difference between sample and population characteristics- in regression can be calculated in excel

187
Q

What can be SE be used to calculate?

A

Confidence interval given a confidence level

188
Q

What is the confidence interval for slope coefficient?

A

(b-2s.e. b +2s.e)

189
Q

What is Anova?

A

Analysis of variance- test for multiple samples from same n

190
Q

Why are degrees of freedom useful?

A

In finding the critical value in the table

191
Q

Degrees of freedom regression

A

K-1

192
Q

Degrees of freedom

A

N-K

193
Q

Degreees of freedom

A

N-1

194
Q

What is the significance level

A

P value

195
Q

How do you find the T stat for the intercept?

A

a/s.e

196
Q

How do you find the t stat for the x variable?

A

b/s.e.

197
Q

What does 0.004 p value means

A

4% chance the relationship occurred randomly

198
Q

What does 0.04 p value means

A

4% chance the relationship occurred randomly

199
Q

Typically what does a p value less than 5 or 10% mean?

A

It is significant

200
Q

What are the limitations in regression analysis?

A
  • iinterval data required i.e. continuous
  • Data should be approx. normally distributed
  • Regression equation should not be used to predict values for beyond the limits of original data
  • The relationship is assumed linear shears non linear best fit line may provide better fit
  • Homoscasticty, variance of y about the regression line does not vary markedly
201
Q

How should residuals of regression be approx distributed?

A

normally w mean of 0

202
Q

What should residuals not show?

A

Trend, slope pof regression residuals on x should=0

203
Q

What should residuals not show?

A

Trend, slope of regression residuals on x should=0

Quantitative (1 decks)

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