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| DayneLee | Helpful Hints from Chapter 9 | 0 | Apr 20 2011, 10:33 PM EDT by DayneLee | ||||
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Thread started: Apr 20 2011, 10:33 PM EDT
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Test Statistic (z vs. t)
• When population standard deviation is known, solve for z and use the z-table. • When population standard deviation is unknown (s will be given), solve for t and use the t-table p-value Approach 1. Solve for the test statistic (z or t) using your sample mean (x-bar) 2. Solve for the p-value using z a. If z is positive, subtract the % below the z-score from 1 to get the p-value b. If z is negative, keep the % below the z-score from the table as the p-value c. In either case, if it is a two-tail test, multiply the p-value by 2 3. Solve for the p-value using t a. Find the 2 values for area in the upper tail that your t-value is between, those values compose the range for your p-value b. If it is a two-tail test, multiply the 2 numbers of the range by 2 4. Compare p-value with alpha (level of significance) a. If p-value is > alpha then do not reject the null b. If p-value is < alpha then reject the null Critical Value Approach 1. For a one-tail test, find the z-score that has the significance level below it. 2. If the z-value of your sample mean (x-bar) is positive, then compare to the positive form of the critical value 3. If the z-value of your sample mean (x-bar) is negative, then compare to the negative form of the critical value 4. For a two-tail test, divide the significance level by 2 and then determine the z-values that have that percent above and below 5. If the z-value for your sample mean (x-bar) is less than the negative critical value, reject the null 6. If the z-value for your sample mean (x-bar) is more than the positive critical value, reject the null 7. If the z-value for your sample mean (x-bar) is within/between the positive and negative forms of the critical value, do not reject the null |
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| tutoringcenter | Quiz 2 | 1 | Mar 15 2011, 1:02 PM EDT by tutoringcenter | ||||
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Thread started: Mar 15 2011, 1:01 PM EDT
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1. Consider a sample with a mean of 500 and a standard deviation of 100. What are the z-scores for the following data values: 520, 650, 500, 450, and 280?
2. Consider that the mean price of a customized wooden, shingled backyard structure is $3100 and the standard deviation is $1200. a. What is the z-score for a backyard structure costing $2300? b. What is the z-score for a backyard structure costing $4900? c. Determine whether or not the costs above are outliers. 3. The results of a national survey showed that on average, adults sleep 6.9 hours per night. Suppose that the standard deviation is 1.2 hours. a. Use Chebyshev’s theorem to calculate the percentage of individuals who sleep between 4.5 and 9.3 hours. b. Assume that the number of hours of sleep follows a bell-shaped distribution. Use the empirical rule to determine the percentage of individuals who sleep between 4.5 and 9.3 hours. 4. Show the five-number summary and determine the upper and lower limits for the following data: 5, 15, 18, 10, 8, 12, 16, 10, 6.
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| tutoringcenter | Practice Quiz 1 | 1 | Mar 15 2011, 1:01 PM EDT by tutoringcenter | ||||
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Thread started: Mar 15 2011, 1:00 PM EDT
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1. Consider a sample with data values of 8, 36, 14, 18, and 24. Compute the mean and median.
2. Consider a sample with data values of 15, 9, 14, 11, 19, 23, 20, and 8. Compute the 30th and 45th percentiles. 3. Consider a sample with data values of 6, 26, 46, 36, 16, 56, 76, and 66. Compute the first and third quartiles, then determine the interquartile range (IQR). 4. Consider a sample with data values of 10, 20, 12, 17, and 16. Compute the variance, standard deviation, and coefficient of variation.
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