pbsi 301 exam

Mean

interval

Mean Formula

Median

Ordinal

Compute Median

1. List the values in order

Mode

Nominal

How to Compute the Mode

1. List all the values in a distribution but list each value only once

Nominal measurement

defined by the characteristics of an outcome that fit into one and only one class or category.

Ordinal Measurement

stands for order

Interval measurement

test or an assessment tool is based on some underlying continuum such that we can talk about how much more a higher performance is than a lesser one.

Ratio level of measurement

characterized by the presence of an absolute zero on the scale.

A measure of central tendency for qualitative

categorical

The median and the mean are best used

with Quantitative data

A correlation coefficient

a single number

Computing a simple correlation coefficient

Linear correlation

relation between two variables that shows up on a scatter diagram as the dots roughly following a straight line

Eyeball Method

Perhaps the easiest (but not the most informative) way to interpret the value of a correlation coefficient is by eyeballing it and using the information

The coefficient of determination

r^2

Coefficient of alienation

the amount of variance in one variable that is not accounted for by the variance in another variable

Correlations Limitations

Outliers

Correlation Matrix

a table showing a simple way to report all relevant correlations at once

Reverse causation

the causal direction could be the opposite from what has been hypothesized

Reciprocal Causation

two variables cause each other

Common Causation

x and y are affected by a third variable

Variability

the spread or dispersion of data

Range

most basic measure of variability

Range Issues

Ignores values in the middle

Interquartile Range (IQR)

Q3 - Q1

Standard deviation

reflects how much scores differ from one another

Standard deviation formula

Steps: 1. List each score. It doesn't matter whether the scores are in any particular order

Always report mean and SD together

High SD means

values farther from the mean on average

Low SD means

the data point is close to the mean!

Variance

standard deviation squared

Standard deviation is susceptible to outliers

outliers are two SD from the mean

X-bar ± (c * s)

c = cutoff scores

Where to start with Good Graphs

Frequency distribution

A frequency distribution is

a method of tallying and representing how often certain scores occur

Class Intervals

typically 2

Histogram

a visual representation of the frequency distribution where the frequencies are represented by bars

Density Plots

smoothed histograms

Frequency polygon

shape tracking frequencies

Skew direction

the tail always tells you the direction of the skew. Negative

Kurtosis

the "peakedness" of the distribution

Histograms are for what variables

continuous

Bar Charts are for what variables

categorical

Scatterplots show

the relationship between two quantitative variables on the same individual

Reliability

consistency

Classical Test Theory

observed score = true score + error

Test-retest reliability

used when you want to examine whether a test is reliable over time

Parallel Forms

used when you want to examine the equivalence or similarity between two different forms of the same test

Inter-rater reliability

measure of how much independent raters agree on ratings

Internal consistency reliability

The more pr