two sample test2

two sample test2 - Determine the sample size Section 7.5...

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Determine the sample size Section 7.5 Determine the sample size for estimating difference of sample means. Determine the sample size for estimating difference of sample proportions.

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Determine the sample size for difference of sample means Usually we deal with problems of equal sample size. Namely, finding sample size n for both samples so that the margin of error is controlled within a range. 2 2 2 2 1 2 2 / 2 1 ) ( ) ( ) ( ME z n n Let ME be the margin of error allowed, the formula for sample size is the following. Note that we are using the Z value.
Determine the sample size for difference of sample proportions We also assume equal sample size. Namely, finding sample size n for both samples so that the margin of error is controlled within a range. 2 2 2 1 1 2 2 / 2 1 ) ( ) ( ) ( ME q p q p z n n Let ME be the margin of error allowed, the formula for sample size is the following. Note that we are still using the Z value.

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Example on determine the sample size for difference of sample means Example 7.8: New fertilizer compounds are often advertised with the promise of increased crop yields. Suppose we want to compare the mean yield of wheat when a new fertilizer is used to the mean yield with a fertilizer in common use. The estimate of the difference in mean yield per acre is to be correct to within 0.25 with a confidence level of 95%. If the sample sizes are to be equal, for the number of one-acre plots of wheat assigned to each fertilizer. 1 2
Example on determine the sample size for difference of sample proportions Example 7.9: Experience has shown that the proportion defective for each of the two machines is in the neighborhood of 0.03. If the supervisor wants to estimate the difference in the proportions to within 0.005 using a 95% confidence interval, how many items must be randomly sampled from the production of each machine?

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Inferences About Population Variances Inference about a Population Variance (section 6.7) Inferences about the Variances of Two Populations ( section 7.6)
Chi-Square Distribution We can use the chi-square distribution to develop interval estimates and conduct hypothesis tests about a population variance. The sampling distribution of ( n - 1) s 2 / 2 has a chi- square distribution with (n-1) degree of freedom, whenever a simple random sample of size n is selected from a normal population.

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This note was uploaded on 09/28/2011 for the course STAT METHO 33:623:385 taught by Professor Faridalizadeh during the Spring '11 term at Rutgers.

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two sample test2 - Determine the sample size Section 7.5...

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