Learn by Doing – Proportions (Step 2) Understanding the Test Statistic
Consider the population of part-time college students. Suppose that 60% of this population is female.
Here is the sampling distribution for the proportion of females in random samples of n students. The standard deviation is approximately 0.10. Lines indicate a distance of 1 and 2 standard deviations above and below the mean.
Here is the sampling distribution for the proportion of supporters in random samples of 25 adults. The standard deviation is approximately 0.10.
If we increase the sample size to 100, the standard deviation decreases to approximately 0.05, as shown.
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