Psych Test 1 Flashcards
Descriptive Statistic
Used to organize or summarize a set of data
Inferential Statistic
Used to make interpretations based on data
example: Which brand of cola do people prefer?
Sample
a small subset of a population that is
intended to be representative of the larger population
Population
a group of people or things that have
some critical characteristic in common
Raw Score
a datum point or value that has not been altered in any way. Raw scores are original measurements from surveys, tests, or other instruments that have not been weighted, transformed, or converted into any other form. Raw scores are also called observed scores.
Random Sampling
In principle, all members of the population are equally likely
to become part of the sample
* Hard to do this unless the population is small and manageable
Convenience Sampling
Sample from among individuals who are conveniently available to study
independent variable
A variable that the experimenter manipulates
example: suppose you want to know how the time to
find an object is affected by the number of other objects present
* IV = number of objects present
quasi-independent variable
A variable that the researcher thinks will predict scores on the DV, but that the researcher does not
manipulate
dependent variable
A variable that the experimenter measures
examples: Response time, Accuracy, Score on Depression Scale
continuous variable
A theoretically infinite number of values exist between adjacent units
example: reaction time, length, age
discrete variable
No values exist between adjacent units
* Data are typically whole numbers or category labels
* e.g., college major; number of correct responses on an exam; number of people in household
frequency distribution
Shows the number of times each score occurs within a data set
cumulative frequency distribution
is calculated by adding each frequency from a frequency distribution table to the sum of its predecessors. The last value will always be equal to the total for all observations, since all frequencies will already have been added to the previous total
percentile
values that divide a set of observations into 100 equal parts. The percentile rank is the proportion of values in a distribution that a specific value is greater than or equal to
percentile rank
?
scatterplot
Used to represent relationship between two measured variables
Bar Graph
Categories (levels of the independent variable) are located on the X axis
Histogram
Like bar graphs, but used to represent frequency distributions composed of interval or ratio data
- the bars touch each other
frequency polygon
Very similar to histogram
*Point is plotted at mid-point of each interval
*Points are joined with a line
*Extended to intervals just above and just below end
points of the distribution
positively skewed distribution
most of the scores are found at the
lower values
- looks like this: n___
negatively skewed distribution
most of the scores are found at the
higher values
- looks like __n
Mean
Score below which 50% of the scores in the distribution are found
* i.e., the median splits the distribution exactly in half
* Can be calculated in multiple ways
Median
Score located at the exact mathematical center of a distribution
* Calculated by adding all the scores and dividing by the number
of scores: