Usage of z Table

(a) Find the area under the normal curve between z = 0.71 and z = 1.28 (b) Find the value of zα/2 corresponding to a confidence interval level of 80% . © Find the confidence interval corresponding to a value of zα/2 = 2.17.

Assuming a normal distribution and using zTables, find the zscore corresponding to a. the 75th percentile, b. the 25th percentile, c. the median.

The lifetimes of batteries in a certain application are normally distributed with mean 50 hours and standard deviation 5 hours. Find the probability that a randomly chosen battery lasts between 42 and 52 hours.
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