Flashcards in Ch20Research Deck (29):

1

## What is statistics?

### a discipline in which mathematics and probability are applied in ways that allow researchers to make sense of their data

2

## What is a frequency distribution?

### a tally of the number of times each score is represented in a data set

3

## What are the four ways to represent a frequency distribution?

### 1. frequency distribution with percentages, 2. grouped frequency distribution with percentages, 3. frequency histogram, and 4. stem-and-leaf plot

4

## How is the central tendency represented?

### mean, median, and mode

5

## What is the variability of a data set?

### the amount of spread in the data

6

## How is variability represented?

### range, variance, standard deviation

7

## What is a normal curve?

### a symmetric frequency distribution that can be defined in terms of the mean and standard deviation of a set of data

8

## How is normal distribution represented?

### z Score and percentages of the normal distribution

9

## What is sampling distribution?

### a specific type of normal distribution

10

## How is significant difference represented?

### with a null hypothesis (hypothesis that there is no statistically significant difference)

11

## What is the Alpha Level?

### Conventional level of chance tolerated is 5% (how much probability of drawing an incorrect conclusion they are willing to tolerate (pre-determined))

12

## What information is needed for the determination of statistical probabilities?

###
Magnitude of the differences between groups: If within-group variability and sample size are constant, a larger between-groups difference is associated with a smaller probability that the difference occurred by chance.

Variability within a group: If the between-groups difference and sample size are constant, the differences between groups with lower within-group variability have a lower probability of occurring than the differences between group with within-group variability.

Sample size- The mean of large samples is more stable than a mean of a small sample.

13

## What is the effect size?

### the between-group difference divided by a pooled version of the SD of the groups being compared

14

## What is the purpose for determining effect size?

### allows the relative magnitude of experimental effects to be compared across variables with different measurement characteristics

15

## What is a Type I error?

### if the statistical conclusion is that there is a difference between groups when in fact there is no difference

16

## What is a Type II error?

### occurs when the statistical conclusion is that there is no difference between the groups when in reality there is a difference

17

## What is the probability of Type II error?

### beta (probability of ignoring an important difference when one exists)

18

## What is the power of a test?

### the likelihood that it will detect a difference when one exists; 1 - beta; power is high when the sampling distributions of groups have minimal overlap

19

## What are the four major threats to statistical conclusion validity?

### low power, lack of clinical importance, error rate problems, violated assumptions (and a fifth, failure to use intention-to-treat analysis)

20

## What is a z Score?

### how many standard deviations a measurement is above or below the mean

21

## Frequency Distribution with Percentages

###
Absolute-number of times each score was obtained

Relative-percentage of patients who received that score

Cumulative frequency-adding relative frequencies of scores up to and including the score of interest

Revised-used when there is missing pieces of data (Adjusted or Cumulative)

22

## Group Frequency Distribution with Percentages

###
Placing scores into groups (ex: 31% 33% and 35% would all be placed into 30-39% group)

Disadvantage: information is lost

23

## Frequency histogram

###
height of bar represents frequency of observations in group

Disadvantage: information is lost

24

## Stem and leaf plot

### presents data concisely without losing information in the grouping process

25

## What is central tendency

### A set of data collapsed into a single score that represents the whole set, "descriptive statistics"

26

## What is inferential statistics?

### Used to determine whether or not there are significant differences between groups

27

## Alpha Level of Inflation?

### When researchers contact many tests within a given study, which increases the overall probability of obtaining chance significant differences. Can be corrected by using a more stringent alpha level for each individual test.

28

## Four ways to increase power

###
1. Maximize between-groups differences by controlling extraneous variables and making sure they apply experimental techniques constantly (rigid controls may reduce a study’s external validity because of how much the setting is being controlled)

2. Reduce within-group variability by studying homogenous groups of subjects or by using subjects as their own controls in repeated measurement designs (these strategies may also reduce external validity by narrowing the group of patients to whom the results can be generalized

3. Increase sample size.

4. Select a more liberal alpha level at which to conduct their statistical tests (this method is unlikely to be acceptable in the scientific research community judging the research.

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