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.
The most frequently occurring score in a distribution.
Arithmetic average.
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.
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
2. Less Varibale observations are more reliable than those that are more variable.
3. More cases are better than fewer.
Statistical Significance
When the sample averages are reliable and the difference between them is relatively large
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