Biostats test 1

2 types of statistics

Descriptive

Inferential

Descriptive statistics are calculations that produce a number that _______ or ______ a set of data

summarizes or describes

Examples of descriptive statistics

Mean, median, mode, range, std dev, variance

Inferential statistics are calculations based on measurements from a _____ used to reach a conclusion about a ______,______ population

sample, larger, unmeasured

Population vs Sample

Population: ALL scores of individuals of interest

Sample: scores of a SUBSET of population

Representative sample

scores of subset, goal to explain behavior/characteristics of population

what is the issue with representative sample

too large

What is a parameter

a characteristic of a population; is constant and DOESNT change unless population does

becomes variables

What are 2 types of parameters

Numerical or nominal (categorical)

How is a statistic different than a parameter

Statistics are used to estimate population parameter

they DIFFER from sample to sample (are variable)

Parameters describe _____ while statistics describe ______

Parameters= populations, statistics = sample

Descriptive statistics describe your _____ but allow you to make infrences about _____inferences

sample, population

variable

any measurable characteristic that varies across different situations

score

measurement of a variable

two major types of variables

quantitative

qualitative

What do quantitative variables measure

amount or degree of variable

NUMERIC and CONTINUOUS

Examples of quantitative variables

weight in pounds, length in feet

(have range limits)

time is always a ______ variable

continuous (quantitative)

What do qualitative variables measure

categorical characteristics

• not continuous —> they are discrete

• not numeric

Examples of qualitative characteristics

religions, gender, political affiliations, university classification

2 qualitative scales of measure

nominal and ordinal

What does a nominal scale of measure show

membership in a group (qualitative, not continuous)

Examples of nominal measures

zodiac signs, jersey numbers, occupations

what do ordinal scales of measure show

same as nominal, but have GREATER and LESS than relationships (qualitative, categorical)

Examples of ordinal scales of measure

Pageant contests, race finish places, university classifications

Note: there is an ORDER (ie one better than the other)

2 quantiative scales of measure

interval, ratio

what are interval scales of measure

same characters as nominal and ordinal, but the intervals between each number is equal

EX of interval scales of measure

Temperature, IQ

what are ratio scales of measure

same as interval, nominal, and ordinal BUT has true 0 point (showing absence of variable) —> nothing BELOW zero

EX of ratio scales of measure

height, weight, time, money

confounding variable

type of extraneous variable, varies with IV, can’t see true relationship

simple frequency distribution

ordered arrangement of score that show each scores frequency

grouped frequency distribution

ordered arrangement of scores condensed into MEANINGFUL GROUPS (class intervals)

class intervals

groups of equal sized ranges of data on grouped frequency distribution

abscissa

X axis (horizontal axis)

ordinate

Y axis (vertical)

frequency polygons are used to graph _____ data

quantitative

reflect intersecting point

Histograms are used to graph _____ data, (____ data)

quantitative, discrete

Histograms represent _____ of scores

distribution

Bar graphs are used to graph categories of a ______ variable

qualitative

Looks like a histogram but spaces in between each

line graph (scatterplot) is used to graph relationships between ______

two variables

points reflect intersection of X and Y variables

What do bell-shaped distributions show (aka normal distribution/ normal curve)

Most frequent scores fall close to the mean

Extremes are less common

Skewed distributions occur when

highest frequency scores are not near mean bc of presence of outliers

In positively (right) skewed, most frequency scores are ____ and tail is toward _____

LOW, tail is toward right (high scores)

In negatively (left) skewed, most frequency scores are ____ and tail is toward _____

HIGH, tail is toward LOW scores (left)

in a rectangular (uniform) distribution….

all X values have same frequency

A bimodal graph has…

2 peaks (2 averages)

what type of curve is this

negative skew

what type of curve is this

positive skew