stats exam practice 1 no answers

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Apr 3, 2024

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1. The sample 10, 18, 20 has a standard deviation of 5.29 28 none of the other answers are correct 18.67 4.32 The deviation from mean needs to all add up to zero Remember to do n-1 which would be 3-1 so you get 56/2 S = Square root 56 /2 = 5.29

Standard deviation – how far the data values are from the mean on average. So the further the values are from the mean, the larger the standard deviation will be. Sample standard deviation - X – x bar represents the distance of each value fron the mean we square (x – x bar)^2 because some values may be negative when subtracting from the mean. Ex) score 20 and mean 30, deviation 20 – 30 = -10 We cant take square root of a negative number, so we square each deviation to make it positive. X = data X bar = sample mean Question 2 According to the empirical rule, a bell or mound shaped distribution will have approximately 95% of the data within what number of standard deviations of the mean? 2 none of the other answers are correct 1 4 3

According to the empirical rule (also known as the 68-95-99.7 rule), for a bell-shaped or mound- shaped distribution: • Approximately 68% of the data falls within one standard deviation of the mean. • Approximately 95% of the data falls within two standard deviations of the mean. • Approximately 99.7% of the data falls within three standard deviations of the mean. So, approximately 95% of the data will be within 2 standard deviations of the mean. 3. A manufacturer claims to have built a home stereo speaker that is 4 feet tall but uses an average of only 30 watts of power. A sample of 40 speakers from the manufacturer found that they used an average of 32 watts of power. The appropriate hypotheses to test the manufacturer’s claim are? A. Ho: M=30 versus HA:M=not equal30 B. Ho: M=32 versus HA: M=not equal32 C. Ho: M=30 versus HA:M=32 D. Ho: M=30 versus HA:M>30 E. None of the above Further testing

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The quality of the researcher The null hypothesis The alternative hypothesis Question 5 If the standard deviation of population A is greater than the standard deviation of population B, all other things being equal, the confidence interval for the mean of A should be wider than the confidence interval for the mean of B. narrower than the confidence interval for the mean of B. the same width as the confidence interval for the mean of B none of the other answers are correct Question 6 A company used linear regression to relate the number of units produced each month (X) to the total cost of production each month (Y), and found the equation to be Y = 10,000 + 4X. Production for next month is scheduled at 2,000 units. The forecast for total production cost would be $14,000. $18,000. $8,000. $10,004 none of the other answers are correct

Question 7 You are given a random variable with probability distribution x 0 1 2 p(x) 0.1 0.6 0.3 The expected value of X, E(X), is 1.0 1.5 none of the other answers are correct 0.3 1.2 Question 8 The retail price of a product is $5 per unit and the cost of production is $2 per unit. If the expected number of units sold is 4, the expected profit will be 12 8 28 20 none of the other answers are correct Question 9 If the population is normal, the population standard deviation is known, and the sample size is 15, which table would you use to calculate probabilities of the sample mean? none of the other answers are correct

binomial normal (Z) Poisson Student t Question 10 A private investigator estimates that 30% of his investigations concern asset location. In the next 20 cases, the number involving asset location would be what type of random variable? Poisson Uniform Normal none of the other answers are correct Binomial Question 11 If the p-value is less than a, you: should accept the null hypothesis. should not reject the null hypothesis. none of the other answers are correct should reject the null hypothesis. should not accept the alternative hypothesis. Question 12 You have taken a sample of size 16. You have decided to look at three different statistics: (a) the average of all 16 numbers, (b) the average of four numbers selected at random from the 16, (c) the average of two numbers selected at random from the 16. The population mean is 30. Estimator (a) will be closer on average to 30 than estimator (c). Estimator (b) will be closer on average to 30 than estimator (a).

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none of the other answers are correct Estimator (c) will be closer on average to 30 than estimator (b). All three estimators are equally accurate. Question 13 A researcher is studying the registered voters in Los Angeles County to see if they favor the Democratic candidate in the next election. He asks 450 voters to tell him if they would vote for the Democratic candidate. Out of this group 285 said they would. The population is all the voters in Los Angeles County. all the voters in favor of the Democratic candidate. the 285 voters in favor of the Democratic candidate. none of the other answers are correct the 450 voters. Question 14 A CNN poll indicated that 56% of those surveyed were in favor of a proposed change in capital gains taxes. The 56% is a parameter. population. none of the other answers are correct sample. statistic. Question 15 The U.S. Census Bureau collects data on household incomes. What would be the most appropriate graphical display tool? a pie chart. a control chart. a scatter diagram.

none of the other answers are correct a histogram. Question 16 Which of the following is NOT quantitative data? the percentage of births born out of wedlock the number of customers entering a mall in 24 hours the zip code of California Lottery winners this year the number of freeway fatalities in Los Angeles County this month none of the other answers are correct