Question

# A) About _____% of the area under the curve of the standard normal distribution is outside...

A) About _____% of the area under the curve of the standard normal distribution is outside the interval z=[−2.08,2.08]z=[-2.08,2.08] (or beyond 2.08 standard deviations of the mean).

B) Assume that the readings at freezing on a batch of thermometers are normally distributed with a mean of 0°C and a standard deviation of 1.00°C. A single thermometer is randomly selected and tested. Find the probability of obtaining a reading less than -0.491°C.

P(Z<−0.491)=P(Z<-0.491)=

C) In a recent year, the Better Business Bureau settled 75% of complaints they received. (Source: USA Today, March 2, 2009) You have been hired by the Bureau to investigate complaints this year involving computer stores. You plan to select a random sample of complaints to estimate the proportion of complaints the Bureau is able to settle. Assume the population proportion of complaints settled for the computer stores is the 0.75, as mentioned above. Suppose your sample size is 205. What is the probability that the sample proportion will be at least 2 percent more than the population proportion?

Note: You should carefully round any z-values you calculate to at least 4 decimal places to match wamap's approach and calculations.

The probabilites values are obtained from T1-83 calculator for all the three subquestions. For the third sub question we use the margin of error formula and calculate the critical value first and then the p value is obtained based on this critical value.

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