# Genetics and Statistics | Summary and Q&A

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August 14, 2014
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MIT OpenCourseWare
Genetics and Statistics

## TL;DR

Analyzing coin flips and genetic phenotypes using the Chi Square Test helps determine if the observed results are statistically significant.

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### Q: What is the purpose of the Chi Square Test for Goodness of Fit?

The Chi Square Test helps determine if sample data comes from an expected population distribution, by comparing observed and expected values for categorical data.

### Q: How is the Chi Square statistic calculated?

The Chi Square statistic measures the discrepancy between observed and expected counts, with each deviation squared and divided by the expected value to normalize the differences.

### Q: What does it mean to fail to reject the null hypothesis?

If the probability of the Chi Square value is greater than the level of significance (e.g., 0.05), the null hypothesis is supported, indicating that the observed results are close enough to the expected values.

### Q: How can the Chi Square test be used in genetic experiments?

The Chi Square test can evaluate the deviation between observed and expected phenotypic ratios, helping researchers determine if factors other than random chance are influencing the results.

## Summary & Key Takeaways

• This video explains how the Chi Square Test for Goodness of Fit can be used to analyze categorical data, such as coin flipping experiments and genetic crosses.

• The video provides steps to calculate the Chi Square statistic and interpret the results, including comparing the test statistic to the Chi Square distribution.

• Two examples are discussed: analyzing the fairness of a coin based on the observed distribution of heads and tails, and evaluating the ratio of mutant to wild type flies in a genetic cross.