Epi Bio Exam 1 (MC)

What starts with the general case (population or model) and then predicts what would happen in many samples?

Probability

What starts with one set of data (sample) and makes inferences about the overall population or model?

Statistics

What variable is the experimental/predictor variable that can be manipulated in an experiment?

Independent variable

What variable is defined as the outcome variable?

Dependent variable

Blood typing is an example of what kind of variable?

Nominal

What variable is defined as categorical outcomes with more than 2 possible outcomes?

Nominal

What variable is defined as categorical outcomes with 2 distinct possible outcomes?

Binomial

Yes/No is an example of what kind of variable?

Binomial

What variable expresses ranks and is influenced by order?

Ordinal

A pain scale measures what kind of variable?

Ordinal

What variable represents data capable of possessing any value in a given range?

Continuous

Blood pressure is an example of what kind of variable?

Continuous

IQ is an example of what kind of variable?

Interval

T/F: The zero point is NOT considered meaningful in an interval variable

True

T/F: The zero point is NOT considered meaningful in ratio variables

False

Temperature in Kelvin is considered what kind of variable?

Ratio

What type of variable can you NOT calculate medians and percentiles?

Nominal

What types of variables can you add or subtract?

Ratio and interval

What types of variables can you calculate median, SD, and SEM?

Ratio and interval

What is the ONLY variable that you can calculate a coefficient of variable?

Ratio

Which of the following is NOT influenced by outliers?

Median

T/F: The mean is influenced by outliers

True

T/F: The median is influenced by outliers

False

What is the benefit of a trimmed mean?

Removes influence from outliers

Which of the following is FALSE about the mode?

Not useful with variables that can only be expressed as integers

T/F: Bias is only caused by the preconceived notions of the experimenter

False

Error is used to refer to _________

Variability

Biased measurements tend to result from what?

Systematic errors

Which of the following terms is defined as the variation among values expressed in the same units as the data?

Standard deviation

1 SD is equivalent to what percentage?

68%

2 SD is equivalent to what percentage?

95%

3 SD is equivalent to what percentage?

99%

What does it mean when the Gaussian distribution curve is called a standard normal curve?

Mean= 0, SD= 1

T/F: The larger the sample size, the smaller the SEM

True

Which of the following statements is FALSE?

The SEM is a measure of the spread of the data

The confidence interval (CI) of a mean is computed by what 4 values?

Sample mean, SD, Sample size, Degree of confidence

The width of the CI is ______ to the sample SD.

Proportional

The CI is ________ to the square root of the sample size.

Inversely proportional

The CI is ________ to the degree of confidence.

Proportional

5 assumptions are accepted when interpreting a CI of a mean. If one of the assumptions is violated, what is the effect?

The true CI will be wider than the calculated CI, the true Cl will be too optimistic

The median is equal to the ______ percentile.

50th

T/F: The SD can be negative.

False

T/F: All bell-shaped curves are Gaussian

False

T/F: The Gaussian distribution is bell-shaped

True

T/F: A 99% CI is wider than a 90% CI

True

What 2 values affect the SEM?

Sample size and SD

T/F: The SEM is always smaller than the SD

True

What is the effect of increasing the sample size on SD?

No effect

Which of the following does the CI size (width) NOT depend on?

Sample median

What term is defined as the two ends of a confidence interval (CI)?

Confidence limits

Which of the following is an example of censored survival data?

All of the above

What method accounts for censored patients when creating a survival table?

Kaplan-Meier

What is the preferred method for creating a survival table, unless the sample size is very large?

Kaplan-Meier

T/F: Pooled data is independent

False

T/F: Patients who die before treatment should not be removed from a survival analysis

True

Why is the median survival time reported instead of the mean survival time?

All of the above

A p-value of ______ is almost universally regarded as the cutoff level for statistical significance.

0.05

T/F: The smaller the p-value, the stronger the evidence to dispute the null hypothesis

True

When the null hypothesis is rejected, the result is said to be __________

Statistically significant

If the p value is less than 0.05, you ________ the null hypothesis

Reject

T/F: The p value is the probability that the null hypothesis is true

False

T/F: The p value is the same as the Type I error rate

False

What error is the incorrect rejection of the true null hypothesis?

Type I

What error is also called a false positive?

Type I

What error is incorrectly retaining a false null hypothesis?

Type II

What error is a false negative?

Type II

T/F: The p value conveys information regarding the size of the observed effect

False

The _____ variables or endpoints in a study, the more likely one of them will come up statistically significant by chance alone

More

T/F: A result with p=0.004 is more statistically significant than a result with p=0.04

False

If you set an α very low, you will make _____ Type I errors

Few

If you set an α very low, you will make _____ Type II errors

More

If the CI for the difference between two means does not include _____ (the null hypothesis), then the result must be statistically significant

0

If the CI for the ratio of two proportions does not include _____ (the null hypothesis), then the result must be statistically significant

1

T/F: Not statistically different means no difference

False

T/F: A high p value proves the null hypothesis

False

If sample size is increased by a factor of 16, CI is expected to narrow by a factor of _____

4

As the power increases, the chances of a Type II error _______

Decreases

T/F: P values can be negative

False

T/F: The concept of statistical hypothesis testing is about making decisions

True

Which of the following is NOT computed from the data?

α value

According to the Familywise Error Rate, more comparisons will lead to a larger chance for a ________

Type I error (false +)

What is the Bonferroni correction?

Divide the α value by number of comparisons

The Bonferroni correction increases the risk for a ________

Type 2 error (false -)

What type of tests quantify how much a data set deviates from the expectations of a Gaussian distribution?

Normality tests

T/F: A normality test can prove the data were sampled from a Gaussian distribution

False

What would fail a normality test?

Small p value

Which of the following should you do if the data fail a normality test?

All of the above

What test is used for non-normal, more robust distributions?

Non-parametric test

What is the simplest robust statistic?

Median

T/F: A normality test asks whether a particular set of data is Gaussian

False

T/F: Outliers may be removed in some instances

True

What test compares the observed and expected numbers of each subject?

Chi square test

What term is defined as the rate of new cases of disease?

Incidence

What term is defined as the fraction of the group that has the disease?

Prevalence

What test compares the prevalence of disease between 2 groups?

Cross sectional study

2 groups of subjects (one with exposure & one without) are observed overtime to determine the incidence rates. What type of study is this?

Prospective study

A single sample of subjects are randomly divided into 2 groups and each group gets a different treatment. Outcomes/Incidences are observed. What study is this?

Experimental study

Two groups of subjects are selected: one with the disease and the other without. Investigators look back to determine possible risk factors. What study is this?

Case control study

How do you calculate the number needed to treat (NNT)?

Take the reciprocal of the absolute risk reduction

Are higher or lower NNT preferred?

Lower