PCM: Biostatistics 2

Question 1

Name the two phases to statistical analysis.

Answer 1

Descriptive statistics and statistical inference

Question 2

______ statistics are used to describe key study variables. Whereas ____________ is employed to make generalizations or to draw inferences about larger populations based on study data.

Answer 2

Descriptive; statistical inference

Question 3

The simplest study has how many primary outcome variables?

Answer 3

One

Question 4

For analytic purposes, variables are classified as ______ or discrete.

Answer 4

continuous

Question 5

_____ variables, sometimes called quantitative or measurement variables, assume any value between a theoretical min and max. For example protein expression levels and serum biomarkers.

Answer 5

Continuous

Question 6

_______ variables can be thought of as having a fixed number of categories. For example the categories male or female.

Answer 6

Discrete

Question 7

Descriptive stats for continuous variables should always include a measure of location (i.e. the mean), and a measure of _________ (i.e. the standard deviation).

Answer 7

Variability

Question 8

What is the appropriate measure of a typical value in the presence of extremes that may inflate the SD or Mean?

Answer 8

Median (i.e. the value that holds 50% of the values above it and 50% of the values below it)

Question 9

For a normal distribution, the range (min-max) is approx. equal to the mean plus or minus ______ standard deviations. Any variables beyond that are considered extremes (outliers).

Answer 9

3 SDs

Question 10

Limit the number of decimal places in tables to ______ decimal place(s) more than the original unit of measurement, so as not to overstate the precision of the analysis.

Answer 10

one

Question 11

In relation to graphical displays, __________ plots are most appropriate for continuous outcomes.

Answer 11

Box-and-whisker plots

Question 12

In relation to graphical analysis, ________ are the most appropriate for ordinal outcomes.

Answer 12

Histograms

Question 13

In relation to graphical analysis, ________ are the most appropriate for categorical outcomes.

Answer 13

Bar charts

Question 14

________ plots are appropriate when both variables are continuous.

Answer 14

Scatter plots

Question 15

The ____________ refers to the entity on which measurements are made. For example, an individual.

Answer 15

Unit of analysis

Question 16

_________ groups are physically separate and are comprised of distinct sampling units (e.g. different experimental units assigned to the active drug versus placebo).

Answer 16

Independent groups

Question 17

_________, matched, or paired groups are often produced when teh same sampling units are measured twice (e.g. before and after an exposure) or when the sampling units are paired (e.g. siblings, litter mates).

Answer 17

Dependent groups

Question 18

Name the two general areas of statistical inference.

Answer 18

Estimation and hypothesis testing

Question 19

In ________ of statistical inference, we generate confidence interval population parameters based on sample data appropriately accounting for sampling variability.

Answer 19

estimation

Question 20

In ______________ of statistical inference, we formally compare population parameters based on sample data, again accounting for sampling variability. We set up competing hypotheses (null and research hypotheses).

Answer 20

Hypothesis testing

Question 21

The null hypothesis represents:

Answer 21

That there will be no difference or no effect between two outcomes based on separate (although possibly identical or non-identical) treatment.

Question 22

The research hypothesis is:

Answer 22

States the anticipated or hypothesized difference or effect outcome between two identical or non-identical treatments.

Question 23

_________ is the probability of observing a test statistic as large or larger than that observed if the null hypothesis were true.

Answer 23

The p value

Question 24

A small p value, <________, would suggest that there is less than a 5% probability of observing a difference as large or larger than that observed in the study sample.

Answer 24

p value <0.05

Question 25

A p value <0.05 would likely lead to rejection or acceptance of the null hypothesis in favor of the research hypothesis?

Answer 25

Rejection, in favor of the research hypothesis.

Question 26

__________-sample studies are most useful when investigating new techniques or technologies.

Answer 26

One-sample

Question 27

Is confidence interval proportional to sample size?

Answer 27

No, inversely proportional. As sample size goes up, 95% confidence intervals tend to shrink in size.

Question 28

When there are more than two independent groups, the procedure to test for differences in means is _______.

Answer 28

Analysis of variance (ANOVA)

Question 29

T/F: in ANOVA, there are >2 independent groups, variances among groups are assumed to be equal and data are assumed to follow a normal distribution.

Answer 29

True

Question 30

If your number of independent sampling units is 5 and you are going to take 6 measurements of each over the period of the study, you will use this type of analysis:

Answer 30

Repeated-measures ANOVA

Question 31

When there are two or more independent groups and the outcome is dichotomous, the procedure to test for differences in proportions is the ________ test.

Answer 31

Chi-square test