(b) Find the 80th percentile of the pecan tree height distribution. (round the answer to 2 decimal
places)
12. Based on the performance of all individuals who tested between July 1, 2012 and June 30,
2015, the GRE Quantitative Reasoning scores are normally distributed with a mean of 152.47
and a standard deviation of 8.93. (https://www.ets.org/s/gre/pdf/gre_guide_table1a.pdf). Show
all work. Just the answer, without supporting work, will receive no credit.
(a) Consider all random samples of 36 test scores. What is the standard deviation of the sample
means? (Round your answer to three decimal places)
(b) What is the probability that 36 randomly selected test scores will have a mean test score that
is between 148 and 152?
13. A survey showed that 1200 of the 1600 adult respondents believe in global warming.
Construct a 95% confidence interval estimate of the proportion of adults believing in global
warming. Show all work. Just the answer, without supporting work, will receive no credit.
14. A city built a new parking garage in a business district. For a random sample of 100 days,
daily fees collected averaged $2,000, with a standard deviation of $500. Construct a 90%
confidence interval estimate of the mean daily income this parking garage generates. Show all
work. Just the answer, without supporting work, will receive no credit
15. A researcher claims the proportion of auto accidents that involve teenage drivers is less
than 20%. ABC Insurance Company checks police records on 200 randomly selected auto
accidents and notes that teenagers were at the wheel in 32 of them.
Assume the company wants to use a 0.05 significance level to test the researcher’s claim.
1. (a) Identify the null hypothesis and the alternative hypothesis.