Problem regarding the proportion of samples

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1. A population of disk drives manufactured by a certain company runs with mean seek time of 10 milliseconds with standard deviation of 0.1 milliseconds. What proportion of samples of size 250 would you expect to result in a mean less than 9 milliseconds? What assumptions do we need to make?

2. Suppose that the national norm of a science test for 12th graders on a particular year has a mean of 215 and a standard deviation of 35.

(a) A random sample of 55 12th graders is selected. What is the probability that this group will average more than 230?

(b) A random sample of 200 12th graders is selected. What is the probability that this group will average over 230?

(c) A random sample of 35 12th graders is selected. What is the probability that this group will average over 230?

(d) How does the sample size in?uence the probability?

Reference no: EM13965218

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