Internal validity is the extent to which you are able to say that no other variables apart from the independent variable caused a change in the dependent variable .

range, variance, standard deviation.

is concerned with objectivity, tight controls over the research situation, and the ability to generalize findings. (Numbers!)

Mean, Medium, and Mode

is the variable the experimenter manipulates or changes.

External validity means the ability that results translate to the real world, findings are generalizable, and results can be translate into another context.

A descriptive statistic that measures the variability by calculating the square root of the variance.

Experimental and Non experimental research

The sum of all values in a data set (group), divided by the number of values in the data set (group).

is the variable being tested and measured in an experiment, and is 'dependent' on the independent variable.

Everyone in the population has equal chance of being selected – random assignment (high external validity)

The p-value represents the probability that the observed relationship in the sample could be due to sampling error
To be set at less than the level of significance (<.05 or <.01)

Attempts to determine the extent of a relationship between two or more variables.

Nominal, Ordinal, Interval, Ratio

Floor effects is the situation in which a large proportion of participants perform very poorly on a task or other evaluative measure, thus skewing the distribution of scores and making it impossible to differentiate among the many individuals at that low level.

The tendency for people who get
high scores on a particular measure to score
closer to the mean (lower) if they are tested
again (and vice versa).

Addiction has a negative impact on marital satisfaction (directional).

are exactly the same as true experiments except they do not have random assignment to all conditions.

Test-retest reliability measures the consistency of results when you repeat the same test on the same sample at a different point in time. You use it when you are measuring something that you expect to stay constant in your sample.

Different groups compared at the same time.

History, Maturation, Mortality, testing effect, instrument decay, selection bias.

Null – represents no relationship between the variables you are studying (Nothing going on!)

Randomized Controlled Trial; the “gold- standard” (RCT).
Two or more groups (e.g., treatment vs treatment control)
One variable is changed/manipulated - all others remain constant.

An instrument must be reliable in order to be valid. For an instrument to be valid, it must consistently give the same score. However, an instrument may be reliable but not valid: it may consistently give the same score, but the score might not reflect a person's actual score on the variable.

Same group compared over time.