Flashcards in Ch23Research Deck (18):

1

## What is correlation?

### the value an individual exhibits on one variable is related to the value he or she exhibits on another variable; CORRELATION IS NOT CAUSATION

2

## What is the most frequently used correlation coefficient?

### the Pearson product moment correlation

3

## What are the other correlation coefficients?

### Spearman's rho and Kendall's tau used with ranked or ordinal #s; phi, Cramer's V, and kappa used for nominal data

4

## What are the major assumptions of correlation coefficients?

### 1 relationships between variables are assumed to be linear, 2 homoscedasticity, 3 both variables have enough variability to demonstrate a relationship

5

## How are correlation coefficients interpreted?

### 1 the strength of the coefficient itself, 2 the variance shared by the two variables, 3 the statistical significance of the correlation coefficient, 4 the confidence intervals about the correlation coefficient

6

## What is correlation coefficient?

### Magnitude and direction of the relationship between variables expressed mathematically

7

## What is the Pearson product moment correlation?

### (r) The average of the cross-products of the z scores for the X and Y variables, ex: relationship between functional variable such as gait velocity and physical impairment variable such as knew flexion ROM in patients with TKA

8

## range for correlation coefficient

### -1 (inversely negative) to +1 (directly positive)

9

## When do you use Spearmans's Rho and Kendall's tau correlations?

### when both variables are ranked or ordinal

10

## When do you use point-biserial correlation?

### with one continuous and one dichotomous variable

11

## What correlation coefficients are used with nominal data?

### phi, Cramer's V and kappa

12

## Strength of coefficient

###
Assumes that the meaningfulness of a correlation is the same regardless of context

.00 - .25 Little of any correlation

.26 - .49 Low correlation

.50 - .69 Moderate correlation

.70 - .89 High correlation

.90 – 1.00 Very high correlation

13

## What is the coefficient of determination?

###
square of the correlation coefficient, (r^2)

The coefficient of determination is an indication of the percentage of variance that is shared by the two variables

14

## What is the statistical significance of the coefficient?

### The probability that the calculated correlation coefficient would have occurred by chance if there was no relationship between the variables

15

## How do you calculate the confidence interval around the coefficient?

### Converts the r values into z scores, calculates confidence intervals with the z scores, and transforms the z score intervals back into a range of r scores

16

## Limits of interpretation

### Interpretation of correlation coefficients should not extend beyond the range of the original data

17

## What is linear regression?

### Prediction of future characteristics from previously collected data; a line showing best fit between variables; variables must be defined as IV or DV

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