Mock exam

Question 1

In an even sample size which ones the mean

Answer 1

mean is midway between the two middle values

Question 2

In an odd sample size which ones is the mean

Answer 2

mean is the middle number

Question 3

which value is the upper quartile

Answer 3

75%

Question 4

which value is the lower quartile

Answer 4

25%

Question 5

where do 50% of values lies between

Answer 5

between the upper and lower quartile

Question 6

does sample mean equal population mean

Answer 6

no - sample mean varies from sample to sample whereas population mean is a fixed value

Question 7

what happens to the widths of the confidence intervals as sample size increases

Answer 7

confidence intervals decrease as the estimate gets better/more precise so confidence interval narrows

Question 8

what is the confidence interval for a mean

Answer 8

estimate of the mean - given in a range rather than a single value

Question 9

what does standard error measure

Answer 9

how well a sample mean estimates the corresponding population quantity/mean

Question 10

what does standard deviation measure

Answer 10

measures the spread of the population or sample

Question 11

if a p-value is less than 0.05 what do you with null hypothesis

Answer 11

reject it

Question 12

if a p value is above 0.05 what do you do with null hypothesis

Answer 12

accept the null hypothesis as there is no evidence against it, but we cannot say that it is true

Question 13

is the data normally distributed for an unpaired t test

Answer 13

yes

Question 14

is the data normally distributed for a paired t test

Answer 14

no, only necessary for the within pairs differences to follow a normal distribution

Question 15

if a sample size increases by x what happens to the confidence intervals

Answer 15

they are reduced by the square root of x, not x

Question 16

what do we use to assume normality during a regression analysis

Answer 16

residuals

Question 17

what is another way to assume normality

Answer 17

inspect the y-values but you will not be taking proper account of the way the mean of the observations changes with x

Question 18

what does the interquartile range measure

Answer 18

the spread of the data

Question 19

how do you estimate the standard error of a sample

Answer 19

take standard error of the current sample and divide it by the square root of the factor the sample increases by

Question 20

a 95% confidence interval for the mean of a large sample is approximately

Answer 20

the sample mean + or - 2 x standard error

Question 21

what indicates a good agreement using the bland altman method of agreement

Answer 21

small bias, narrow limits of agreement, most data points falling within the limits

Question 22

how do we test the association between response and predictor variables in regression analysis

Answer 22

use a t test built using the estimated regression coefficient and its standard error

Question 23

what does an odds ratio of > 1 mean

Answer 23

condition is more likely in exposed subjects

Question 24

what does a odds ration < 1 mean

Answer 24

less likely to be exposed

Question 25

what does an odds ratio of 1 mean

Answer 25

equally like to be exposed/unexposed

Question 26

what do we know about the standard deviation of the variation about the regression line

Answer 26

assumed to be constant, known as homeoscedasticity.
If the assumption is violated then the regression may be invalid

Question 27

when data is highly positively skewed

Answer 27

the mean is greater than the median
lower tail is shorter than the upper tail
usually one or more extreme values

Question 28

what does pearson correlation coefficient show when it’s negative and significant

Answer 28

increase in one variable means a decrease in another variable

Question 29

what does cohen kappa do

Answer 29

calculation that corrects for chances of agreement, range of values between -1 and 1

Question 30

what does a chi2 test do

Answer 30

it is used to test for associations rather than agreement

Question 31

what is chi2 test applied to

Answer 31

it is applied to frequencies (actual counts) not percentages

Question 32

what happens to standard error of mean and standard error of proportion when sample size increases

Answer 32

they both get smaller

Question 33

what does the logit function do

Answer 33

used in regression
natural logarithmic transformation of the odds, natural log of the odds is the logit of probability of event or condition

Question 34

what is logistic regression applicable to

Answer 34

a binary response variable with any number of predictors, categorical or continuous