Two additives to Portland cement are being tested for their effect on the strength ofconcrete. 21 batches were made with Additive A, and their strengths showed standarddeviation s, = 41.3. 16 batches were made with the same percentage of Additive B,and their strengths showed standard deviation s, = 26.2. Assume that the strengths ofconcrete follow a normal distribution. Is there evidence at the 1% level of signifi-cance that the concrete made with Additive A is more variable than concrete madewith Additive B?

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Answered: Two additives to Portland cement are…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 251.5 and a standard deviation of 69.1. (All units are 1000 cells/uL.) Using the empirical rule, find each approximate percentage below. a. What is the approximate percentage of women with platelet counts within 3 standard deviations of the mean, or between 44.2 and 458.8? b. What is the approximate percentage of women with platelet counts between 113.3 and 389.7? a. Approximately% of women in this group have platelet counts within 3 standard deviations of the mean, or between 44.2 and 458.8. (Type an integer or a decimal. Do not round.) b. Approximately % of women in this group have platelet counts between 113.3 and 389.7. (Type an integer or a decimal. Do not round.)
A sample of 33 lights in Austin gives an average of 46 cars/min while the city SD=3.4 A sample of 34 Dallas lights give a mean of 44 cars/mim with the city SD=1.4 At the 91% level, do the towns differ? 1. Is the test (A-Left Tailed, B-Right Tailed, C-2-Tailed) (separate with comma if there are 2) 2. Critical Value 3. Test statistic 4. 3-decimal p-Value
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The physical plant at the main campus of a large state university recieves daily requests to replace florecent lightbulbs. The distribution of the number of daily requests is bell-shaped and has a mean of 60 and a standard deviation of 3. Using the empirical rule (as presented in the book), what is the approximate percentage of lightbulb replacement requests numbering between 57 and 60? Do not enter the percent symbol. % ans =
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The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 260.4 and a standard deviation of 60.2. (All units are 1000 cells/uL.) Using the empirical rule, find each approximate percentage below. a. What is the approximate percentage of women with platelet counts within 3 standard deviations of the mean, or between 79.8 and 441.0? b. What is the approximate percentage of women with platelet counts between 140.0 and 380.8? ..I. a. Approximately % of women in this group have platelet counts within 3 standard deviations of the mean, or between 79.8 and 441.0. (Type an integer or a decimal. Do not round.)

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