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Suppose students' ages follow a skewed right distribution with a mean of 21 years old and a standard deviation of 2 years If we randomly sample 450 students. which of the following statements about the sampling distribution. of the sample mean age is incorrect? The shape of the sampling distribution is approximately normal. The mean of the sampling dntributlon it approximately 21 years old. The standard deviation of the sampling distribution it equal to 2 years. All are incorrect X it normally distributed around mean of 50 with a standard deviation of 20 Then the chance that X is negative is .0062 .6554 .9938 .0244 The length of time a traffic signal stays green (nicknamed the "green time") at a particular intersection follows a normal probability distribution with a mean of 200 seconds and the standard deviation of 10 seconds Use this information to answer the following questions. Which of the following describes the derivation of the sampling distribution of the sample mean? The standard deviations of a large number of samples of size n randomly selected from the population of "green times" are calculated and their probabilities are plotted. The mean and median of a large randomly selected sample of "green times" are calculated Depending on whether or not the population of "green times" is normally distributed, either the mean or the median is chosen as the best measurement of center. A single sample of sufficiently large size is randomly selected from the population of "green times" and its probability is determined. The means of a large number of samples of size n randomly selected from the population of "green times" are calculated and their probabilities are plotted. Calculate the mean for the discrete probability distribution shown here 5.25 4.50 4.00 5.00 A recent study suggested that 70%. of all eligible voters will vote in the next presidential election. Suppose 20 eligible voters were randomly selected from the population of all eligible voters. Which of the following is necessary for this problem to be analyzed using the binomial random variable? There are two outcomes possible for each of the 20 voters sampled. The outcomes of the 20 voters must be considered independent of one another. The probability a voter will actually vote is 0.70. the probability they wont is 0.30. I only III only I, II, and III II only The diameter of hall bearings produced in a manufacturing process can be explained using a uniform distribution over the interval 3.5 to 5.5 millimeters. What is the mean diameter produced in this manufacturing process? 4.0 millimeters 4.5 millimeters 5.0 millimeters 5.5 millimeters
Explanation / Answer
!).A
2).P(z<0-50/20)
or P(Z<-2.5)
=0.0062
answer is A
3).C
4).mean = sumation x*p(x)
= 2*0.2+4*0.4+5*0.3+10*0.1
= 4.5
ans-B
5).C
6,.mean=3.5+5.5/2
=4.5
ans- B
