Terms  Definitions 

Direct relationship 
In this kind of relationship, those who score high on one variable tend to score higher on the other, & vice versa

Positive relationship 
See direct relationship

Indirect (inverse) relationship 
Those who score high on one variable tend to score high on another.

Negative relationship 
See inverse relationship

Causal relationship 
Est correlation does not necessarily establish causal relationship.

Pearson product moment correlation coefficient 
The full, formal name of pearson's r. Ranges from 1.00 to 1.00. Both 1.00 and 1.00 indicate a perfect relationship.

Interpretation of pearson's r 
Varies depending on type of study.

Pearson's r 
Not a proportion. Thus multiplying it by 100 does not yield a percentage.

Test reliability 
One way to examine test reliability is to administer the same test twice to a group of participants without trying to change the participants between administrations of the test  then correlate.

Coefficient of determination 
r squared. When r2 is converted to a percentage it indicates how much variance on one variable is accounted for by the variance on the other.

Variance. 
Spread

Variance explained 
r2 x 100. Aka variance accounted for.

Scattergram 
Illustrates correlation between two variables.

Outliers 
Exception to the overall trend.

Multiple correlation coefficient 
The symbol for a multiple correlation coefficient is upper case italicize R. A multiple correlation coefficient has the same basic characteristics as r. Determines the degree of relationship between a culmination of two predictors.

Linear Regression 
A Regression analysis that assumes that the predictor variable is related to the criterion variable through a linear function

Truncated range 
A range of cases that lacks one or both ends of the distribution of values

Restricted range 
Limitation by researcher– Via sampling, measuring Procedures, or other aspects of experimental design – of the full range of total possible scores that may be obtained to only a narrow, limited portion of that total

Curvilinear correlation 
A functional relationship between variables that is not a straight line form when depicted graphically

Random sampling 
yields an unbiased sample; names can be drawn to obtain a random sample; a table of random numbers may also be used to draw a random sample; to use a table of random numbers give each person in the population number name

Stratified random sample 
Draw participants at random separately From each stratum

Multistage random samples 
May be used in largescale studies

Random cluster sampling 
Existing groups of participants are drawn. All members of population must belong to a cluster

Sampling Errors 
A random sample may differ from a population in important aspects by the luck of the draw

Sample size 
The larger the sample, the smaller the sampling errors and the greater the precision; increasing sample size produces diminishing returns; the smaller the anticipated difference in the population the larger the sample should be; for populations with very limited variability even small samples can yield concise results. The more variable the population the larger the sample size should be. When studying a rare phenomenon large samples are usually required. Large samples do not correct Four bias

Precision 
The larger the sample the smaller the sampling errors and the greater the precision

Central limit theorem 
According to this theorem the sampling distribution of Means is normal

Standard error of the mean 
The standard deviation of the sampling distribution is known as the standard error of the mean

Sampling distribution of mains 
A large number of means

Margin of error 
The standard error of the main is a margin of error

Confidence interval for a mean 
Confidence interval assist and interpreting means that are subject to random errors. they cannot take bias into account. Using large samples keeps the standard error of the mean and the confidence interval small

Point estimate 
A single estimated numerical value of the population parameter

Interval estimate 
An estimate range of likely values for a given population parameter

Observed difference 
The difference a researcher Obtains. It may not represent the true difference because of the influence of random sampling error.

Significance tests 
Test of the null hypothesis

P value 
Significance level. The probability of rejecting the null hypothesis when it is in fact true. – Such as making a type one error

Alpha level 
The probability level for rejecting the null hypothesis

Decision error 
Type one error: reject the null hypothesis when it is true – type two error: felt to reject the no hypothesis when it does false

About the population 
Testing the null hypothesis about the population

One tailed significance test 
For directional hypothesis

Twotailed significance test 
nondirectional hypothesis

T test 
Tests the difference between two sample means for significance

Statistically significant 
Hey synonym with rejecting the null hypothesis

Not significant (n.s.) 
Failure to reject the null

r 
Symbol for Pearson product moment correlation coefficient

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