Stat Chapter 2 Flashcards

Frequency Distributions

raw score

a data point that has not yet been transformed/analyzed

frequency distribution

describes the pattern of a set of numbers by displaying a count/proportion for each possible value of a variable - have to display every #

frequency table

a visual depiction how often each value occurred - values in the 1st column, and the numbers of individuals with scores at that value are listed in the 2nd column

outlier

an extreme score that is either very high/very low in comparison with the rest of the scores in the sample

grouped frequency table

a visual depiction of data that reports frequencies within a given interval rather than the frequencies for a specific value

histogram

a graph that looks like a bar graph but depicts just one variable, usually based on continuous data, with the values of the variable on the x-axis and the frequencies on the y-axis

normal distribution

a specific frequency distribution that is a bell-shaped, symmetrical, unimodal curve

skewed distribution

a distribution in which one of the tails of the distribution is pulled away from the center

positively skewed data

the distribution’s tail extends to the right, in a positive direction

floor effect

a situation in which a constraint prevents a variable from taking values below a certain point

negatively skewed data

distribution with a tail that extends to the left, in a negative direction

ceiling effect

a situation in which a constraint prevents a variable from taking on values above a given number, ex; test too easy

dot plot

a graph that displays each data point in a sample, with the range of scores along the x-axis and a dot for each data point above the appropriate value

unimodal

one peak

bimodal

two peaks

multimodal

many peaks

uniform rectangular

no peaks

leptokurtic distribution

a distribution that has fatter tails and a higher, sharper peak than a normal distribution

platykurtic

has negative excess kurtosis, meaning it has thinner tails and a flatter peak compared to a normal distribution