To run a Chi-Squared Test for Independence in real-life situations, here's a simple guide to follow:
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Set Up Your Hypotheses:
- Null Hypothesis (H0): This means the two groups you are looking at are not connected or related.
- Alternative Hypothesis (Ha): This means the two groups are connected or related in some way.
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Gather Your Data:
- Put your data into a table called a contingency table.
- This table should show how often things happen for each group you are studying.
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Calculate Expected Frequencies:
- For each box in the table, figure out how many occurrences we would expect to see, using this formula:
- Eij=GrandTotal(RowTotali)(ColumnTotalj)
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Compute Chi-Squared Value:
- To find the Chi-Squared statistic, use this formula:
- χ2=∑Eij(Oij−Eij)2
- Here, Oij stands for the actual counts you collected.
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Determine Degrees of Freedom:
- Calculate degrees of freedom using this formula:
- df=(r−1)(c−1)
- Here, r is the number of rows in your table and c is the number of columns.
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Find the Critical Value:
- Look in a Chi-Squared distribution table to find the critical value at your chosen level of significance (for example, α=0.05).
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Make Your Decision:
- If your Chi-Squared value (χ2) is greater than the critical value, reject the null hypothesis (H0).
- If the Chi-Squared value is less than or equal to the critical value, you do not reject the null hypothesis.
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Conclude Your Findings:
- Wrap up your results by explaining whether the two groups are independent or dependent. Also, include the p-value where it makes sense.