7. The Environmental Protection Agency took soil samples at 16 randomly selected
ID: 3218788 • Letter: 7
Question
7. The Environmental Protection Agency took soil samples at 16 randomly selected locations within a 3-mile radius of a former industrial waste dump and checked each for lead levels. Lead levels above 1200 ppm are considered unsafe. They found the mean lead level in their samples to be 650 ppm. Identify the parameter and statistic. a) Parameter 650 ppm; Statistic 1200 ppm b) Parameter 1200 ppm; Statistic 650 ppm c) Parameter-16 randomly selected locations; Statistic-mean lead level in 3-mile radius d) Parameter mean lead level in 3-mile radius; Statistic 650 ppm e) Parameter mean lead level in 3-mile radius; Statistic-1200 ppm 8. By the Central Limit Theorem, when a large random sample is taken, the sample mean, y, is Normally distributed with which mean and standard deviation? a) Mean y: Standard deviation s/vn b) Means standard deviation o/ c) Mean k Standard deviation sl d) Mean Standard deviation /vm 9. It is generally believed that electrical problems affect about 14% of new cars. An automobile mechanic conducts diagnostic tests on 128 new cars on the lot. How many successes (electrical failures) do you expect? a) 1.28 b) 17.92 c) 110.08 d) Cannot determine from information given 10. Heights of adult men are Normally distributed. A random sam of 13 adult men is taken. How is the sample mean height y distributed? a) Normal, by the Central Limit Theorem b) Normal, because the underlying population distribution is Normal c) Normal, by the 68-95-99.7 rule d) skewed, because the sample size is under 30 e) Unable to determine from the given information 11. A95% confidence interval for p can be interpreted to mean that if we take 100 random samples of the same size and construct 100 such confidence intervals for p, then a. On average 95 of them will include p b. On average 95 of them will include p c. Exactly 95 of them will include p d. Exactly 95 of them will include p 12. Which conditions would make a confidence interval narrower? CIRCLE THREE. a. Higher confidence level b, Lower confidence level c, Larger sample size d. Smaller sample size e. Larger standard deviation f, Smaller standard deviationExplanation / Answer
Q.7 Parameters are numbers that summarize data for an entire population. Statistics are numbers that summarize data from a sample, i.e. some subset of the entire population.
So parametere is here mean lead - level in 3mile radius
Statistic = 650ppm
Option D
Q.8 Mean = y' and standard deviation = /sqrt(n) [ OptionB]
Q.9 success = np = 128 * 0.14 = 17.92 ( option b)
Q>10 Unable to determine from the given information
Q>11 a 95% confidence interval means that on average 95 of them will include p^.
Q.12 (a) higher confidence level
(c) larger sample size
(f) smaller standard deviation
as confidence interval is +- Zalphas/sqrt(n)
Q. 13 Accpet Null Hypothesis, as it is under the given significance level so we accpet null hypothesis. Option c is correct
Q.14 +-0.04 = +-1.65 * sqrt(0.7 * 0.3/n)
n = 356 [ option d]
Q.15 P - value is the probability of given statistic, given that the alternative is true
!Q.16 P(CGPA < 2.93; 3.02, 0.29) =
Z - value = ( 2.93 - 3.02)/ 0.29 = -0.31
so P(CGPA < 2.93; 3.02, 0.29) = 0.3783
THe mean of the sample of 20 students selected is 2.93 and lower = (2.93 - 3.02)/ (0.29/sqrt(20)
= -0.09/ 0.06484 = -1.388
so P(Xbar < 2.93) = 0.0823
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