Psych Stats Exam 1

Statistics

the product of numbers and procedures

Descriptive Statistics

used to describe a sample

Inferential Statistics

used to draw conclusions about the population

Sample

a group of people who belong to the population that is being measured

Population

the entire group in question

Parameter

describes the population

Variable

anything we can measure that has more than one value

Qualitative Variable

indicates a category or classification

Quantitative Variable

indicates an amount of quantity

Independent Variable

the variable that is being changed

Dependent Variable

the variable that is being measured

Measurement

the systematic and orderly assignment of numerical value to a variable

Ratio Scale

has magnitude, equal intervals, AND absolute zeros

Interval Scale

has magnitude and equal intervals

Ordinal Scale

has magnitude

Nominal Scale

used for QUALITATIVE variables

Frequency Distribution

a set of scores or data organized by frequency

Simple Frequency (f)

scores are organized by simple frequencies (the count of each value)

Relative Frequency (rel. f)

dividing the frequency of each score by the total number of scores

Cumulative Frequency (cf)

reflects the frequency of scores in that distribution equal to and below that score

Cumulative Percentage (c%)

the cumulative frequency divided by N

Percentile Rank (P)

indicates the percentage of the scores in a distribution that are equal to and below that score

Percentile Point (X)

we want to know what score represents a certain percentile rank

Normal Distribution

the bell curve

Skewed Distribution

the tails are more pronounced on one end rather than both ends

Symmetrical Distribution

the distribution has a clear middle point and looks the same on both sides

Bimodal Distribution

there are two highest frequencies on either side of the middle

Order of Operations

Parentheses, Exponents/Square roots, Multiply, Divide, Add, Subtract

Real Limits

represents the range of values that could be rounded to get the whole number (+ and - 0.5)

Rounding

Interpolation

1. we assume that multiple occurrences of a score are actually different values within the real limits of that number

2. we assume that the multiple occurrences are equally distant from each other

Central Tendency

the general tendency for most of the scores to lie at or near the center of the distribution

Mean

average

Median

the midpoint

Mode

the score that occurs most frequently

Variability

the extent to which the scores in a distribution deviate from the central tendency or from one another

Range

the difference between the highest and lowest scores in a distribution

Variance

the average squared difference from the mean

Standard Deviation

the average distance from the mean