Ch20Research

Question 1

What is statistics?

Answer 1

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

Question 2

What is a frequency distribution?

Answer 2

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

Question 3

What are the four ways to represent a frequency distribution?

Answer 3

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

Question 4

How is the central tendency represented?

Answer 4

mean, median, and mode

Question 5

What is the variability of a data set?

Answer 5

the amount of spread in the data

Question 6

How is variability represented?

Answer 6

range, variance, standard deviation

Question 7

What is a normal curve?

Answer 7

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

Question 8

How is normal distribution represented?

Answer 8

z Score and percentages of the normal distribution

Question 9

What is sampling distribution?

Answer 9

a specific type of normal distribution

Question 10

How is significant difference represented?

Answer 10

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

Question 11

What is the Alpha Level?

Answer 11

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

Question 12

What information is needed for the determination of statistical probabilities?

Answer 12

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.

Question 13

What is the effect size?

Answer 13

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

Question 14

What is the purpose for determining effect size?

Answer 14

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

Question 15

What is a Type I error?

Answer 15

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

Question 16

What is a Type II error?

Answer 16

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

Question 17

What is the probability of Type II error?

Answer 17

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

Question 18

What is the power of a test?

Answer 18

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

Question 19

What are the four major threats to statistical conclusion validity?

Answer 19

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

Question 20

What is a z Score?

Answer 20

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

Question 21

Frequency Distribution with Percentages

Answer 21

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)

Question 22

Group Frequency Distribution with Percentages

Answer 22

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

Question 23

Frequency histogram

Answer 23

height of bar represents frequency of observations in group

Disadvantage: information is lost

Question 24

Stem and leaf plot

Answer 24

presents data concisely without losing information in the grouping process

Question 25

What is central tendency

Answer 25

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

Question 26

What is inferential statistics?

Answer 26

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

Question 27

Alpha Level of Inflation?

Answer 27

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.

Question 28

Four ways to increase power

Answer 28

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.

Question 29

What are power tables used for?

Answer 29

To determine what sample size is needed to achieve a particular level of power.
Variables needed: desired power, alpha level used, estimate of between-groups difference that is considered clinically meaningful and an estimate of the within-group variability expected