Statistical Reasoning

After getting data, we have to organize, analyze, and interpret it.

Describing Data

After getting data, we have to organize it into groups.

Watch Out for Marketers

People can manipulate a graph depending on what they want to emphasize. (Read the labels on the graph!)

Measures of Central Tendency

Used to summarize data.

Mode

The most frequently occurring score in a distribution.

Mean

Arithmetic average.

Median

The middle score in a distribution.

Skewed Distributions

Illustrates three tendencies but deceptively high income balance.

Measures of Variation

Amount of variation is how similar or diverse the scores are.

Range

Difference between the highest number and lowest score

Standard Deviation

A computed measure of h ow much scores vary around the mean score.

Reliability of Observed Differences

When is it safe to generalize from a sample?

1. Representative Samples are Better than Biased Samples

Description

2. Less Varibale observations are more reliable than those that are more variable.

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3. More cases are better than fewer.

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Statistical Significance

When the sample averages are reliable and the difference between them is relatively large