Inferential Statistics and Experimental Research

Question 1

INFERENTIAL STATISTICS

Answer 1

INFERENTIAL STATISTICS

Question 2

Descriptive statistics are used to describe ______ while Inferential statistics are used to make decision about the __________ group based on the information of the ________ group.

Answer 2

• data

- population, sample

Question 3

In descriptive statistics you use mean (SD) for _________ data and count (percent) for __________ data.

Answer 3

• continuous

- categorical

Question 4

What is the difference between population and sample?

Answer 4

Population

• contains all subjects of interest
• impractical
• numerical property = parameter (pop mean, proportion)

Sample

• part of selection that s required to be random
• best approach available
• quantity from it = statistic (sample mean, proportion)

Question 5

Sample selection is required to be ______ but might not be good because random selection doesn’t gaurantee proportional representation of all parts of the population.

Answer 5

random

Question 6

• The standard deviation of sample means is called what?

- What is the formula for this?

Answer 6

• SEM (standard error of the mean)

- s/sqrt (n) where s=the sample SD and n=sample size

Question 7

What does the Central Limit Theorem state?

Answer 7

Sampling distribution of the sample means approaches a normal distribution as the sample size gets larger.

Question 8

The SEM for a smaller sample size is typically _______ than that of a larger sample size. What does this mean?

Answer 8

larger, means there is more variability

Question 9

What are the 2 common methodologies for inferential statistics?

Answer 9

• Statistical Hypothesis Testing (SHT)

- Confidence Interval (CI)

Question 10

What are some common uses of inferential statistics?

Answer 10

• estimate population parameters

- compare effects between groups

Question 11

What are the 4 steps of the procedure for SHT?

Answer 11

1. ) State the statistical hypothesis (null and alternative hypothesis)
2. ) Select a level of significance (α)
3. ) Decide which test to use (t-test, analysis of variance, Mann-Whitney U Test, chi-square test, McNemar test)
4. ) Make a decision to reject or retain the null hypothesis based on resulting quantity called p-value

Question 12

What is the difference between null and alternative hypothesis?

Answer 12

Null Hypothesis
-group means are not different
Alternative Hypothesis
-there is a true difference between groups, and the treatment was effective

Question 13

What is a p-value?

Answer 13

Major resulting value of running a statistical hypothesis test and quantifies how consistent your sample values are with the null hypothesis.

Question 14

The p value ranges from 0-1. What does a large p-value mean? What does a small p-value mean?

Answer 14

• Large p-value- your sample values are consistent with the null hypothesis
• Small p-value- your sample values are not consistent with the null hypothesis

Question 15

For a p-value (α) level <0.05 you _______ the null hypothesis. What does this mean?

Answer 15

• Reject

- This means that the observed difference shows significant effect

Question 16

For a p-value (α) level >0.05 you _______ the null hypothesis. What does this mean?

Answer 16

• Retain

- This means the observed difference is probably due to chance and is not significant

Question 17

Difference between a Type I and Type II error?

Answer 17

Type I = rejection of a true null hypothesis

Type II = non-rejection of a false null hypothesis

Question 18

What is a confidence interval?

Answer 18

A range of values so defined that there is a specified probability that the value of a parameter lies within it.

Question 19

Confidence Interval Example:
Fitzgerald et al estimated the population mean for lumbar spinal extension for 30-39 year old individuals. Based on the random sample of 42 individuals, they determined that mean=40.0 degrees and sd=8.8 degrees. How can you tell how accurate this estimate is?

• Find the SEM.
• Assess the 95% confidence interval.

Answer 19

SEM
=sd/sqrt (n) = 8.8/sqrt(42) = 1.36

CI
=(40-21.36),(40+21.36)
=37.3 - 42.7

Question 20

• A narrower CI implies higher ________ with less ___________.
• A wider CI implies lower __________ with increased ___________.

Answer 20

• precision, variability

- precision, coverage (variability)

Question 21

CI can be used to estimate population parameters, but it can also be used to compare effects between ________.

Answer 21

groups

Question 22

CI can be used to compare between groups based on the __________ or the ______.

Answer 22

• mean difference

- ratio

Question 23

The effect is not significant if the CI contains the ___________. The effect is significant if the CI doesn’t contain the _________.

Answer 23

• null value

- null value

Question 24

• Null Value for the Mean Difference = _____

- Null Value for the Ratio = ______

Answer 24

• 0

- 1

Question 25

The mean difference of SBP was 10 and its 95% CI was (5.2, 15.7). Is the difference significant?

Answer 25

Yes, CI does not contain null value.

Question 26

The odds ratio of having not been physically active for patients with breast cancer over the controls was 2 and its 95% CI was (0.5, 4.5). Is the difference significant?

Answer 26

No, Ci contains the null value.

Question 27

Summary for Inferential Statistics: - The purpose of using inferential statistics is to make decision about the _________ group based on the information of the _______ group - Sampling errors are the differences between the ________ values and the _______ values - Sample mean together with its standard error can picture what the sampling distribution looks like and can provide an interval _______ for the population mean - ________________ is performed to make a decision about the population by rejecting or retaining the null hypothesis based on the resulting quantity called p-value - ______ as a result of running a statistical hypothesis testing is used to make decision - In a statistical hypothesis testing are the potential errors including type _ and type __ errors - Confidence interval for the mean difference is checked for inclusion of its null value of __ for the significant effect - Confidence interval for the ratio is checked for including of its null value of __ for the significant effect

Answer 27

- population, sample - sample, population - estimate - SHT (statistical hypothesis testing) - p-value - Type I (reject true null), Type II (non-rej of false null) - 0 - 1

Question 28

EXPERIMENTAL RESEARCH

Answer 28

EXPERIMENTAL RESEARCH

Question 29

What is the purpose of experimental research?

Answer 29

Provide a structure for evaluating the cause-and-effect relationship between a set of independent and dependent variables.

Question 30

The term ________ _____ is often used to describe experimental studies that examine the effect of intervention on human subjects.

Answer 30

Clinical Trial

Question 31

What are the 4 phases of Clinical Trials?

Answer 31

Phase I -Show safety on small sample of subjects, help to understand mechanism of action. Phase II -Once shown to be safe, this phase demonstrates effectiveness on relatively small samples. Phase III -Randomized, usually blind, experiment comparing against a placebo. Large scale studies with 100s or 1000s of subjects. Phase IV -Once approved by FDA, this phase involves continual investigation on its effects.

Question 32

What is considered the gold standard of true experimental designs?

Answer 32

RCT

Question 33

What is the difference between a True-Experimental Design and a Quasi-Experimental Design?

Answer 33

True-Experimental Design - subjects are randomly assigned - at least 2 comparison groups Quasi-Experimental Design - does not meet the requirements of a true experiment - lacking random assignment or comparison groups, or both - used when a true-experimental design is not feasible - accommodates for the limitations of natural settings

Question 34

What is the difference between Between-Subjects Design and Within-Subject Design?

Answer 34

Between-Subjects Design - subjects randomly assigned to independent groups - completely randomized designs Within-Subjects Design - subjects act as their own control - repeated measures design

Question 35

Difference between Single-Factor Design and Multi-Factor Design?

Answer 35

Single-Factor Design (one-way design) - structures the investigation of one independent variable - easy to develop - can't account for simultaneous interactions of several variables Multi-Factor Design (multi-way design) - incorporates two or more independent variables - can name variously

Question 36

Pretest-Posttest Control Group Design is the basic structure of a _________ and compares two or more groups that are formed by _______ assignment.

Answer 36

- RCT | - random

Question 37

What is considered the scientific standard in clinical research for establishing a cause-and-effect relationship?

Answer 37

Pretest-Posttest Control Group Design

Question 38

When is a Posttest Only Control Group Design used?

Answer 38

When a pretest is impractical or potentially reactive.

Question 39

_____________ design involves the ability to control the potential influence of individual differences and uses subjects as their own control.

Answer 39

Repeated Measures Design

Question 40

Repeated Measures Design has a potential for _________ effects and ________ effects. This design is only used when the outcome measure will revert back to baseline between interventions.

Answer 40

- practice | - carryover

Question 41

What is a Crossovere Design?

Answer 41

Half the subjects receive treatment A followed by B; half receive treatment B followed by A.

Question 42

Crossover Design is only used when patient's condition will not change over time and is not a reasonable approach when treatment effects are _____. _______ period is essential.

Answer 42

- slow | - Washout

Question 43

Mixed Design has both the _______-subjects and _________-subjects factors.

Answer 43

within-subjects and between-subjects

Question 44

Summary For Experimental Research: - Experimental research provides a structure for evaluating the ______________ relationship between a set of independent and dependent variables - In true experimental design subjects are ________ assigned to at least two comparison groups - When a true-experimental design is not feasible, ____-experimental design is useful lacking random assignment or comparison groups, or both - In between-subjects design subjects are _______ assigned to independent groups - In within-subjects design subjects act as their own ________ - By the number of independent variables (=factors), design can be _______-factor or ______-factor - _______-_______ design compares the changes from pre- to post- test for two or more groups that are formed by random assignment - When a pretest is either impractical or potentially reactive, _________ only design is useful - Repeated measures design and crossover design are the types of _______-subject design - Mixed design is available when you have _____ the within-subjects factors and between-subjects factors

Answer 44

- cause-and-effect - randomly - quasi - randomly - control - single-factor or multi-factor - pretest-posttest - posttest - within - both