Psy 3187 Midterm

Ordinal Scale

A scale of measurement using ranks rather than actual numbers. (1st, 2nd, 3rd)

Std Dev of sample

subtract mean from each number, square the answers and add them up, divide by the number of points - 1, then take the square root of it

Std Dev of population

subtract mean from each number, square the answers and add them up, divide by the number of points, then take the square root of it

Mean vs. Standard Deviation

the mean shows you where the scores are located. The standard deviation shows you how far apart the scores are from each other and from their mean.

Z Score formula

x - mean / std dev

Median formula

(N+1)th / 2

Histogram

Continuous data

Descriptive Statistics vs. Inferential Statistics

Descriptive statistics uses the data to provide descriptions of the population. Inferential statistics makes inferences and predictions about a population based on a sample of data taken from the population in question.

Bar Graph

Discrete data

Mean formula

Frequency x Midpoints / N

Mode vs. Median vs. Mean

Mode: Most common number Median: Middle number Mean: Average

Parameter vs. Statistic

Parameter: a characteristic or measure of a POPULATION Statistic: a characteristic or measure of SAMPLE

Platykurtic vs. Leptokurtic

Plato: flatter and more spread out than a normal curve Lepto: very tall, thin, and peaked curve

Population vs. Sample

The population is the whole group while a sample are parts of the population.

Interval Scale

a scale that demonstrates absolute differences between each scale point (sat score, pH)

Central Tendency vs. Variability

Variability describes how the numbers deviate from one another while the Central Tendency describes the typical value (mean median mode)

Best to use mean when

data is continuous and symmetrical

Best to use median when

data is ordinal and skewed

Qualitative vs. Quantitative

descriptions vs. numbers and measurements

On the graph....

longest line is mode next is median then mean

X formula

m + std dev(Z)

Left Skewed

mean < median

Right Skewed

mean > median

Ratio Scale

measurement that has a natural, or absolute, zero. Zero matters (weight, money)

when finding SD prime never.... only....

never add or subtract... only multiple or divide

Nominal Scale

numbers are assigned to objects or classes of objects solely for the purpose of identification (gender, age)

Best to use mode when

ordinal or categorical data