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