A human resources department is comparing two employee training programs to see if they lead to different pass rates on a required certification exam. They randomly select two groups of employees. In Program A, 16 out of 20 employees passed the exam. In Program B, 30 out of 40 employees passed. Are the basic conditions met to conduct a 2-proportion hypothesis test?
Table of contents
- 1. Introduction to Statistics53m
- 2. Describing Data with Tables and Graphs2h 1m
- 3. Describing Data Numerically1h 48m
- 4. Probability2h 26m
- 5. Binomial Distribution & Discrete Random Variables2h 55m
- 6. Normal Distribution & Continuous Random Variables1h 48m
- 7. Sampling Distributions & Confidence Intervals: Mean2h 8m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 20m
- 9. Hypothesis Testing for One Sample2h 23m
- 10. Hypothesis Testing for Two Samples3h 25m
- 11. Correlation1h 6m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 30m
- 14. ANOVA1h 4m
10. Hypothesis Testing for Two Samples
Two Proportions
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The data below is taken from two random, independent samples. Calculate the margin of error for a 99% confidence interval for the difference in population proportions.
x1=87, x2=68
n1=120, n2=115
A
0.061
B
0.062
C
0.158
D
0.060

1
Step 1: Begin by calculating the sample proportions for each group. The formula for sample proportion is p̂ = x/n, where x is the number of successes and n is the sample size. For the first sample, calculate p̂₁ = x₁/n₁, and for the second sample, calculate p̂₂ = x₂/n₂.
Step 2: Determine the standard error (SE) for the difference in proportions. The formula for SE is: SE = sqrt((p̂₁(1 - p̂₁)/n₁) + (p̂₂(1 - p̂₂)/n₂)). Substitute the values of p̂₁, p̂₂, n₁, and n₂ into this formula.
Step 3: Identify the z-value corresponding to the desired confidence level. For a 99% confidence interval, the z-value is approximately 2.576. This value is derived from the standard normal distribution table.
Step 4: Calculate the margin of error (ME) using the formula: ME = z * SE. Multiply the z-value by the standard error calculated in Step 2.
Step 5: Interpret the margin of error. The margin of error represents the range within which the true difference in population proportions is likely to fall, given the specified confidence level.
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