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22 Questions with Answer of Statistical Methods - Exam 2 | STA 2023, Exams of Data Analysis & Statistical Methods

Valencia CollegeData Analysis & Statistical Methods

Material Type: Exam; Class: Statistical Methods; Subject: STA: Statistics; University: Valencia Community College; Term: Unknown 1993;

Typology: Exams

Pre 2010

Uploaded on 08/03/2009

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STA 2023 Test #2 Practice Multiple Choice
1. Items produced by a manufacturing process are supposed to weigh 90 grams. The
manufacturing process, however, is such that there is variability in the items
produced and they do not all weigh exactly 90 grams. The distribution of weights
can be approximated by a normal distribution with mean 90 grams and a standard
deviation of 1 gram. What percentage of the items will either weigh less than 87
grams or more than 93 grams?
A) 6%
B) 94%
C) 99.7%
D) 0.3%
2. What is the area under the standard normal curve corresponding to Z < 2.85?
A) .0022
B) .4978
C) .9978
D) .6103
3. A market research company employs a large number of typists to enter data into a
computer. The time taken for new typists to learn the computer system is known
to have a normal distribution with a mean of 90 minutes and a standard deviation
of 18 minutes. The proportion of new typists that take more than two hours to
learn the computer system is
A) 0.952.
B) 0.548.
C) 0.048.
D) 0.452.
4. The distribution of actual weights of 8.0 oz. chocolate bars produced by a certain
machine is normal with a mean of 8.1 oz. and a standard deviation of 0.1 ounces.
The proportion of chocolate bars weighing under 8.0 oz. is
A) 0.500.
B) 0.159.
C) 0.341.
D) 0.841.
5. The scores on a university examination are normally distributed with a mean of
62 and a standard deviation of 11. If the top 15% of students are given A's, what
is the lowest mark that a student can have and still be awarded an A?
A) 51
B) 74
C) 90
D) 93
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STA 2023 Test #2 Practice Multiple Choice

  1. Items produced by a manufacturing process are supposed to weigh 90 grams. The manufacturing process, however, is such that there is variability in the items produced and they do not all weigh exactly 90 grams. The distribution of weights can be approximated by a normal distribution with mean 90 grams and a standard deviation of 1 gram. What percentage of the items will either weigh less than 87 grams or more than 93 grams? A) 6% B) 94% C) 99.7% D) 0.3%
  2. What is the area under the standard normal curve corresponding to Z < 2.85? A). B). C). D).
  3. A market research company employs a large number of typists to enter data into a computer. The time taken for new typists to learn the computer system is known to have a normal distribution with a mean of 90 minutes and a standard deviation of 18 minutes. The proportion of new typists that take more than two hours to learn the computer system is A) 0.952. B) 0.548. C) 0.048. D) 0.452.
  4. The distribution of actual weights of 8.0 oz. chocolate bars produced by a certain machine is normal with a mean of 8.1 oz. and a standard deviation of 0.1 ounces. The proportion of chocolate bars weighing under 8.0 oz. is A) 0.500. B) 0.159. C) 0.341. D) 0.841.
  5. The scores on a university examination are normally distributed with a mean of 62 and a standard deviation of 11. If the top 15% of students are given A's, what is the lowest mark that a student can have and still be awarded an A? A) 51 B) 74 C) 90 D) 93
  1. Let X denote the time taken for a computer link to be made between the terminal in an executive's office and the computer at a remote factory site. It is known that X has a normal distribution with a mean of 15 seconds and a standard deviation of 3 seconds. On 90% of the occasions the computer link is made in less than A) 19.39 seconds. B) 15.95 seconds. C) 11.16 seconds. D) 18.84 seconds.
  2. A soft-drink machine can be regulated so that it discharges an average of μ

ounces per cup. If the ounces of fill are normally distributed with a standard deviation of 0.4 ounces, what value should μ be set at so that 6-ounce cups will overflow only 2% of the time? A) 6. B) 6. C) 5. D) 5.

  1. As part of a promotion for a new type of cracker, free trial samples are offered to shoppers in a local supermarket. The probability that a shopper will buy a packet of crackers after tasting the free sample is 0.20. Different shoppers can be regarded as independent trials. If X is the number of the next 100 shoppers that buy a packet of the crackers after tasting a free sample, then the probability that X exceeds 20 is approximately A) 0. B) 0. C) 0. D) 0.
  2. A random sample of size 25 is to be taken from a population which is normally distributed with mean 60 and standard deviation 10. The average x of the observations in our sample is to be computed. The sampling distribution of x is A) normal with mean 60 and standard deviation 10. B) normal with mean 60 and standard deviation 2. C) normal with mean 60 and standard deviation 0.4. D) normal with mean 12 and standard deviation 2.
  3. A famous result says that in many situations for large sample sizes the sampling distribution of the sample mean is approximately normal. This famous result is A) the law of large numbers. B) the central limit theorem. C) the multiplication rule. D) the 68-95-99.7 rule.
  1. The SAT scores of entering freshmen at University X have a N(1200, 90) distribution and the SAT scores of entering freshmen at University Y have a N(1215, 110) distribution. A random sample of 100 freshmen is sampled from each University, with x the sample mean of the 100 scores from University X and y the sample mean of the 100 scores from University Y. The probability that x is less than 1190 is A) 0.0116. B) 0.1335. C) 0.4090. D) 0.4562.
  2. The SAT scores of entering freshmen at University X have a N(1200, 90) distribution and the SAT scores of entering freshmen at University Y have a N(1215, 110) distribution. A random sample of 100 freshmen is sampled from each University, with x the sample mean of the 100 scores from University X and y the sample mean of the 100 scores from University Y. The probability that y less than 1190 is A) 0.0115. B) 0.1335. C) 0.4090. D) 0.4562.
  3. The scores of individual students on the American College Testing (ACT) Program composite college entrance examination have a normal distribution with mean 18.6 and standard deviation 6.0. At Northside High, 36 seniors take the test. If the scores at this school have the same distribution as national scores, what is the mean of the sampling distribution of the average score for the 36 students? A) 1. B) 3. C) 6. D) 18.
  4. The scores of individual students on the American College Testing (ACT) Program composite college entrance examination have a normal distribution with mean 18.6 and standard deviation 6.0. At Northside High, 36 seniors take the test. The sampling distribution of the average score for the 36 students is A) approximately normal, but the approximation is poor. B) approximately normal, and the approximation is good. C) normal. D) neither normal nor nonnormal. It depends on if the 36 students were randomly selected from all students who took the test.
  1. Lloyd’s Cereal Company packages cereal in 1-pound boxes (1 pound = 16 ounces). It is assumed that the amount of cereal per box varies according to a normal distribution with a mean of 1 pound and a standard deviation of 0. pound. One box is selected at random from the production line every hour, and if the weight is less than 15 ounces, the machine is adjusted to increase the amount of cereal dispensed. The probability that the amount dispensed per box will have to be increased during a 1-hour period is A) 0. B) 0. C) 0. D) 0.
  2. Lloyd’s Cereal Company packages cereal in 1-pound boxes (1 pound = 16 ounces). It is assumed that the amount of cereal per box varies according to a normal distribution. A sample of 16 boxes is selected at random from the production line every hour, and if the average weight is less than 15 ounces, the machine is adjusted to increase the amount of cereal dispensed. If the mean for an hour is 1 pound and the standard deviation is 0.1 pound, the probability that the amount dispensed per box will have to be increased is A) 0. B) 0. C) 0. D) 0.
  3. It is generally believed that nearsightedness affects about 12% of children. A school district gives vision tests to 133 random incoming kindergarten children. What percent of such samples would you expect to have less than 10% of the children be nearsighted? A) 23.89% B) 2.82% C) 2.60% D) 22.10%
  4. It is known that 80% of all cars on the interstate exceed the speed limit. What is the probability that more than 420 out of a random sample of 500 cars exceed the speed limit on the interstate? A) 0. B) 0. C) 0. D) 0.