EPI exam 3 - Week 2!

Question 1

The statistical ability of a study to detect a true difference, IF one truly exists between group-comparisions is what?

Answer 1

Power (1-Betta)

Question 2

Power (1-B) gives us the level of accuracy of what?

Answer 2

Correctly accepting/not accepting the Null Hypothesis.

Question 3

How is Sample Size relevant in detecting if a difference between groups truly exists?

Answer 3

The larger the sample size, the greater the likelihood.

Question 4

What are the three factors that go into sample size determination?

Answer 4

1. Minimum difference between groups deemed significant
2. Expected variation of measurement
3. Type 1 and Type 2 error rates & Confidence Interval.

Question 5

The smaller the difference between groups necessary to be considered significant, the greater the ________ is needed?

Answer 5

Sample Size

Question 6

What must you do with Error rates and Confidence intervals when determining sample size?

Answer 6

Add in anticipated drop-outs or loss to follow up.

Question 7

Statistical tests used to determine possible error-rate or likelihood of chance in comparing difference or relationship between variables is reported as what?

Answer 7

P-value

Question 8

How do we obtain a P-value?

Answer 8

A statistical test critical value is calculated and compared to the appropriate table of probabilities for that test, then a Probability value (P-value) is obtained.

Question 9

The probability value is based on what?

Answer 9

Probability of observing, due to chance alone, a test statistic value as extreme or more extreme than actually observed if groups were similar.

Question 10

When is the probability value selected?

Answer 10

Before the study starts (a priori)

Question 11

If the p value is lower than the pre-selected alpha value (5%) then we say it is _____ and _____

Answer 11

Statistically significant

reject null hypothesis.

Question 12

If we reject a null hypothesis the risk of what type of error is low?

Answer 12

Type 1

Question 13

At baseline you want your p values to be what?

Answer 13

Above (5%) because you want to accept the null hypothesis.

Question 14

Why do you want to accept the null hypothesis at baseline?

Answer 14

Because you do not want your groups to be significantly different until after you have administered your treatment options.

Question 15

Lavene’s Test

Answer 15

Asses whether variances between groups are different.

Question 16

What are the three required assumptions of Interval/Ratio Data for proper selection of parametric test?

Answer 16

1. Normally-distributed
2. Equal variances
3. Randomly-derived & Independent

Question 17

A 95% confidence interval shows what?

Answer 17

We are 95% sure that the true difference or relationship falls within a certain range.

Question 18

If the confidence interval crosses 1.0 for ratios or 0.0 for absolute differences it is significant/not significant?

Answer 18

Not significant

Question 19

What is a forest plot in relation to this lecture?

Answer 19

Another way to show CI information to show whether or not there is a statistical significance to the data.

Question 20

Just because something is statistically significant does not mean it is what?

Answer 20

Clinically equivalent

Question 21

What is the first question you must ask when deciding what kind of statistical test to run?

Answer 21

What data level is being recorded? Followed by does the data have order/magnitude and does the data have a equal consistent distance along the entire scale?

Question 22

What does the first question of selecting the correct statistical test give you?

Answer 22

The type of data we are working with.

Question 23

What is the second question you must ask yourself when selecting the appropriate statistical test?

Answer 23

What type of comparison/assessment is desired.

Question 24

What is a correlation test?

Answer 24

Provides a quantitative measure of the strength and direction of a relationship between variables. It is given with a -1 to +1 range.

Question 25

What is a partial correlation?

Answer 25

A correlation that controls for confounding variables.

Question 26

What is the nominal correlation test?

Answer 26

Contigency Coefficient

Question 27

What is the Ordinal Correlation test?

Answer 27

Spearman Correlation

Question 28

Pearson Correlation is for which data type?

Answer 28

Interval

Question 29

If the P value is greater than a 0.05 in the pearson correlation it means what?

Answer 29

There are no linear correlations present, but there may be non-linear correlations present.

Question 30

All correlations can be run as what to control for confounders?

Answer 30

Partial correlations