Statistics - Sampling & Central tendencies

Question 1

Standard deviation indication

Answer 1

shows spread between numbers & how volatile they are

In same unit as data set

Question 2

Variance indication

Answer 2

average degree to which points deviate from the mean (in squared units)

Question 3

Outlier

Answer 3

any data that lies an abnormal distance from the given data

Question 4

Extrapolating

Answer 4

estimating a value outside the given data range

Question 5

Interpolating

Answer 5

estimating value inside the given data range

Question 6

line of best fit

Answer 6

estimated correlation used for predictions by extrapolating the graph

Question 7

venn diagram

Answer 7

a geometric representation of sets & their relation

Question 7

quartiles

Answer 7

show you were certain percentages of the data lie; 25%, 50%, 75% respectively

Question 7

Outlier test

Answer 7

Q1- 1.5 x IQR = is below Q1
Q3- 1.5xIQR= is below Q3

Question 7

set

Answer 7

collection of well defined unqiue objects

Question 7

list

Answer 7

a collection of objects

Question 7

PMCC

Answer 7

Pearson moment correlation coefficient
* only used for linear equations
* - = negative correlation
* + = positive correlation
* always between 0-1

Question 8

Ogive

Answer 8

cumulative frequency curve

Question 9

central tendency

Answer 9

mean, mode, median = descriptive summary of data

Question 10

Skew

Answer 10

measuring where most data lies
negative skew = most are positive
postitive skew= most are negative

Question 11

Analysing histograms

Answer 11

CSOS
* centre
* spread
* outlier
* shape

Question 12

Shape

Answer 12

• amount of peaks= unimodel, bimodel, multimodal
• symmetry & skew

Question 13

unreliable data

Answer 13

if
* missing data
* errors in handling data

Question 14

sufficient data

Answer 14

if there is enough data to support your conclusion

Question 15

How is standard dev. affected when a constant is added or subtracted

Answer 15

unaffected as all values shift by that number= distance between values remains the same

Question 16

how is standard dev. affected when a constant is multiplied or divided

Answer 16

standrad deviation is also multiplid or divided as this affects the ratio between the distances of the vlaues

Question 17

How is mean affects when a constant is added to a value

Answer 17

constant is also added to mean as it shifts

Question 18

Target population

Answer 18

population from which you take a sample of

Question 19

Sampling Unit

Answer 19

single member that is chosen to be sampled

Question 19

Sampling frame

Answer 19

list of the items/people

Question 20

Sampling values

Answer 20

possible values the sampling variable can take

Question 20

Sampling Variable

Answer 20

variable under investigation

Question 21

BIA's in sampling

Answer 21

* no response * bad design * bias in respondant * some mebers are excluded

Question 22

Reliable data

Answer 22

data is reliable when you can retake it and get the similar results

Question 23

Sufficient data

Answer 23

Data is sufficient if there is enough data available

Question 24

Qualitative Data

Answer 24

* opinion based * expressed in words * can be described * ONLY mode can be calculated

Question 25

Quantitative data

Answer 25

* expressed in numbers * can be discrete or continuous * can be measured * can be counted

Question 26

Discrete data

Answer 26

* countable * in disctinct catagories * finite value Types of graph * dotted graph * bar chart

Question 27

Continuous data

Answer 27

* measureble * can always be measured more accurately and to higher resolution * infinite value Graph * histogram * graph (example cumulative frequency)

Question 28

Simple random sampling

Answer 28

Sampling units are assigned numbers and a random number generator is used Pros * everyone has equal chance of being chosen = bias free * simple & cheap Cons * not suitable for large population * needs sampling frame

Question 28

Systematic Sampling

Answer 28

You take the population/sampling frame= k assign numbers on everyone and start between 1- k; take every kth member Pros * simple & quick to use * suitable for large sample sizes Cons * might be biased when you chose who to start on * sampling frame needed

Question 28

Quota Sampling

Answer 28

Split sample into groups based on qualities handpick one item from each group until quota is satisfied Pros * ensures variety in sample * allows small groups to be represented * no sampling frame required Cons * biased in choosing = not random

Question 28

Stratified sampling

Answer 28

put items in stratas with common characteristics find startas proportion within population = strata/population perform random sampling in each strata Pros * random * represnets different groups reflective in the population proportionally cons * needs smapling frame * same cons as random within each strata

Question 28

Convenience sampling

Answer 28

find whoever is most convenient/closest proximity Pros * easy & inexpensive Cons * unreflective of use in sample * highly biased

Question 28

Clustered sampling

Answer 28

put people into random groups of different kinds of people select individual group randomly only choose one from each group

Question 29

things to remember when making box plots

Answer 29

Check for outliers

Question 30

Estimating mean ( or any measures of cnetral tendency)

Answer 30

* in frequency list take mean of range value * use same frequency * plot in spreadsheet = calculate

Question 31

finding measures of cnetral tendency on GDC

Answer 31

* plot list (x/frequency) * click menu * click stats * click stat calc * click one variable calc * done :D