Statistics

Question 1

What is sampling?

Answer 1

randomnly take a small set of data from a huge set to be investigated

Question 2

What are the two aspects of sampling?

Answer 2

randomisation and size

Question 3

What are the two types of samples?

Answer 3

Independent or dependent

Question 4

How to decide a population size?

Answer 4

depends on the research aim

Question 5

What information is needed to estimate sample size?

Answer 5

clinical difference in practice

standard deviation from previous/pilot studies

Question 6

How to decide sample size?

Answer 6

difference in means of 80% in medical research

0.05 significance level

Question 7

Ideal sample size

Answer 7

larger than 10 and ideal is 30

Question 8

What is a double blind experiment?

Answer 8

nobody knows what the f is going on

Question 9

How do we know if data is normal distribution?

Answer 9

skewness coefficient, >2EM means its not normal distribution
P-p plot- dots arent around the line its not normal distribution
Kolomogorov-smirnov- if the significance is below 0.05 its not normal distribution

Question 10

What is the null hypothesis?

Answer 10

G1 and G2 arent stastically different

If the tested results are <0.01 or 0.05 then reject the null hypothesis

Question 11

When do you accept the null hypothesis?

Answer 11

p>0.05

Question 12

what is the t-test?

Answer 12

parametric test with a parameter similar to normal distribution
used to compare two groups of data

Question 13

what is an applied situation for a t-test

Answer 13

to compare means for two groups of data with small sample size or data distribution should be normal

Question 14

When is ANOVA used?

Answer 14

when more than two means are compared with one another, if its just two then the t-test is used

Question 15

what is degree of freedom?

Answer 15

n-1

Question 16

what is variance?

Answer 16

descriptor to show how far away samples are from the data center
standard deviation squared

Question 17

what is an independent sample t-test?

Answer 17

two samples from different populations regarding the same variable

Question 18

what is paired t-test?

Answer 18

two sample means from the same population measuring the same variable at two different times e.g. pre and post test

Question 19

what is variance?

Answer 19

similar to standard deviation and is a descriptor to show how far away the data is from the center
standard deviation squared

Question 20

what are the two variances?

Answer 20

variance within group shows differences amongst samples and variances between groups shows differences between groups

Question 21

what is the mean of squared differences between groups and within groups

Answer 21

between groups= differences between group mean and total mean
within groups= between samples and their group mean

Question 22

what is the F value?

Answer 22

ANOVA uses the F value to test if p value is significant

MS between groups/ MS within groups = f value

Question 23

What are the two test before/after ANOVA?

Answer 23

before- contrast

after- post-hoc

Question 24

how do we describe non-numeric data?

Answer 24

nominal and ordinal data

frequencies, percentages, distribution, charts- pie, bar, histogram, tables etc.

Question 25

what is the chi test?

Answer 25

also called the pearson chi square test compares the observed and expected frequencies in each category to test if all categories contain the similar proportions of values is there a difference between measured and expected values?

Question 26

Is Chi squared a parametric or non-parametric test?

Answer 26

Non parametric

Question 27

What is the expected frequency in a Chi test?

Answer 27

either all are equal or theoretical and the theoritcal depends on your expectation.

Question 28

What is the goodness of fit test?

Answer 28

compares the observed and expected frequencies in each category

Question 29

What is the asym sig?

Answer 29

when calculating the chi value you get a number and then this number will give you the asym sig if the asym sig is <0.05 this is significant

Question 30

In the Chi square test which function of SPSS do they keep going on about?

Answer 30

crosstab function

Question 31

what are the applications and limitations of the chi test?

Answer 31

deals with nominal/ordinal data between two or more variables could be used to compare numeric data but quantitative data could be lost applied condition: almost no limitation in application

Question 32

can t-test be applied to stuff without normal distribution?

Answer 32

no it cannot

Question 33

how to describe normal distribution vs non-normal distribution?

Answer 33

normal- mean and standard deviation | non-normal- median and quartiles

Question 34

what are the two conditions in parametric test?

Answer 34

data to be numeric and normal distribution

Question 35

what are the criterion used in non-parametric tests?

Answer 35

the number of signs | the total of ranks in groups

Question 36

what does the sign test show?

Answer 36

shows which sample is larger rather than the difference between the two

Question 37

What is the wilcox signed ranks test for dependent data?

Answer 37

similar to the paired t-test but for non-normal distribution of data. To do with comparing two groups of medians non-parametric tests

Question 38

what is the mann whitney test?

Answer 38

``` non-parametric data non-numeric data compares two independent groups uses rank data does not require any data ditribution ```

Question 39

talk about the limitations and applications of non-parametric tests

Answer 39

chi, mann whitney and wilcox are the three non-parametric tests used for nominal/ordinal data and to compare two/multiple variables can compare numeric data with non-normal distribution almost no limitations in applications

Question 40

what is the difference between the mann whitney and wilcox?

Answer 40

both are non-parametric tests and involve the summation of ranks whitney- independent samples wilcox- matched/dependent samples

Question 41

what plot can be used to measure whether there is a trend between two variables?

Answer 41

scatter/dot plot

Question 42

what is a correlation coefficient and when is it accepted?

Answer 42

used to describe whether two variables have a linear relationship and how strong that relationship is also called pearssons coefficient if the significance level is <0.05

Question 43

what is the range of vales for the correlation coefficient?

Answer 43

-1 to 1 as the correlation comes closer to 1 its called a positive correlation and as the correlation becomes closer to -1 it becomes a negative correlation correlation of 0 indicates that there is no correlation and the best is a horizontal line through the more closer to 1 the more correlated two values are

Question 44

when is correlation coefficient significant?

Answer 44

when the p value is <0.05 (*) | when the p value is<0.01 (**)

Question 45

describe what the R value <0 and >0 means

Answer 45

<0 - one value decreases while another increases | >0- both values increase

Question 46

what is the intercept?

Answer 46

the point at which the line cuts through the y axis

Question 47

what is linear regression?

Answer 47

``` linear regression considers that there is a linear relationship between two variables independent variable - x dependent variable - y b1- intercept b2- slope ```

Question 48

what is standard error of the estimate?

Answer 48

the range of predicted value

Question 49

what are residuals?

Answer 49

the actual values minus the predicted values - errors produced by the model and the larger this value is the worse it is the sum of squared differences between the actual and predicted value

Question 50

what are the signs for regression and correlation coefficients?

Answer 50

regression coefficient- b1 and b2 | correlation coefficient- R

Question 51

can linear regression be used for non-linear stuff?

Answer 51

if the variables arent linearly related then they can be transformed to a suitable form an then linear regression can be used

Question 52

what are censored cases?

Answer 52

when collecting data some cases cannot be determined/studied outwith factors related to the one being studied

Question 53

what data is needed for survival analysis?

Answer 53

information stopped time analysed factor studied

Question 54

describe survival analysis based on data quality and time period

Answer 54

data quality- the more the samples the better the better the results, if the number of samples isnt enough then dont do the survival analysis time period

Question 55

what is meta-analysis?

Answer 55

a method to use multi source data to analyse what is favoured by most studies provides the whole picture on an arguable issue from multiple sources meanly see the mean and effect size? consider sample size as weight in analysis?

Question 56

what is the odds ratio and how do you calculate it?

Answer 56

odds ration can be used as an estimate when the occurence of the factor is rare

Question 57

in spss which function will give you odds ratio?

Answer 57

RISK function

Question 58

when do you make a forest plot?

Answer 58

meta- analysis

Question 59

define regression

Answer 59

construct an equation to describe the relationship between two or more variables

Question 60

what does the residual tell us about the model?

Answer 60

the lower the resiuals, the more accurate the predicted and the better the model

Question 61

degree of freedom 1 vs 2?

Answer 61

df1 - number of groups - 1 | df2- number of samples- number of groups

Question 62

what is the homogenity of variance test?

Answer 62

to test for the equality of group variances not dependent on the asumptionof normality HV>0.05 the variances are similar otherwise its not