MATH 10 De Anza College Uniform Probability Distribution & Standard Deviation Quiz

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Math 10

De Anza College

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1) The uniform probability distribution is used with a. a continuous random variable b. a discrete random variable c. a normally distributed random variable d. any random variable 2) A continuous random variable is uniformly distributed between a and b. The probability density function between a and b is a. zero b. (a - b) c. (b - a) d. 1/(b - a) Exhibit 6-2 The travel time for a college student traveling between her home and her college is uniformly distributed between 40 and 90 minutes. 3) Refer to Exhibit 6-2. What is the random variable in this experiment? a. the uniform distribution b. 40 minutes c. 90 minutes d. the travel time 4) Refer to Exhibit 6-2. The probability that she will finish her trip in 80 minutes or less is a. 0.02 b. 0.8 c. 0.2 d. 1.00 5) Refer to Exhibit 6-2. The probability that her trip will take exactly 50 minutes is a. zero b. 0.02 c. 0.06 d. 0.20 6) Refer to exhibit 6-2. The 90th percentile corresponding travel time is a. 75 b. 85 c. 60 d. 58 7) A standard normal distribution is a normal distribution with a. a mean of 1 and a standard deviation of 0 b. a mean of 0 and a standard deviation of 1 c. any mean and a standard deviation of 1 d. any mean and any standard deviation 8) For a standard normal distribution, a negative value of z indicates a. a mistake has been made in computations, because z is always positive b. the area corresponding to the z is negative c. the z is to the left of the mean d. the z is to the right of the mean Exhibit 6-6 The life expectancy of a particular brand of tire is normally distributed with a mean of 40,000 and a standard deviation of 5,000 miles. 9) Refer to Exhibit 6-6. What is the random variable in this experiment? a. the life expectancy of this brand of tire b. the normal distribution c. 40,000 miles d. None of the alternative answers is correct. 10) Refer to Exhibit 6-6. What percentage of tires will have a life of 34,000 to 46,000 miles? a. 38.49% b. 76.98% c. 50% d. None of the alternative answers is correct. 11) In point estimation, data from the a. population is used to estimate the population parameter b. sample is used to estimate the population parameter c. sample is used to estimate the sample statistic d. None of the alternative ANSWERS is correct. 12) The probability distribution of all possible values of the sample mean is called the a. central probability distribution b. sampling distribution of the sample mean c. random variation d. standard error 13) As the sample size increases, the a. standard deviation of the population decreases b. population mean increases c. standard error of the mean decreases d. standard error of the mean increases 14) Suppose the average driving distance for the 2011 Masters Golf Tournament was 282.5 yards with a standard deviation of 12.2 yards. A random sample of 30 drives was selected from a total of 4,144 drives that were hit during this tournament. What is the probability that the sample average was 279 yards or less? a) 0.3540 b) 0.2676 c) 0.1611 d) 0.0582 15) A theorem that allows us to use the normal probability distribution to approximate the sampling distribution of sample means and sample proportions whenever the sample size is large is known as the a. approximation theorem b. normal probability theorem c. central limit theorem d. central normality theorem 16) The confidence associated with an interval estimate is called the a. level of significance b. degree of association c. precision d. confidence level 17) A confidence interval is constructed by adding and subtracting a ____________________ to a given point estimate. a. confidence level b. confidence coefficient c. sample standard deviation d. margin of error 18) When a higher confidence level is used, all other parts of the confidence interval held constant, a. the confidence interval will be wider. b. the confidence interval will be less likely to contain the parameter being estimated. c. the confidence interval will be narrower. d. the confidence interval will not be affected. 19) A ________ is defined as the probability that the interval estimate will include the population parameter of interest, such as a mean or a proportion. a) margin of error b) confidence level c) significance level d) confidence interval 20) The critical z-score for a 98% confidence level is ________. a) ± 1.28 b) ± 1.96 c) ± 2.33 d) ± 2.575 21) A random sample of 130 mortgages in the state of California was randomly selected. From this sample, 14 were found to be delinquent on their current payment. The 98% confidence interval for the proportion based on this sample is ________. a) (0.015, 0.201) b) (0.029, 0.188) c) (0.036, 0.280) d) (0.044, 0.172) 22) Apple would like to estimate the web browsing battery life of the iPad. The following data represents the battery life, in hours, experienced by six users. Using this sample, the 95% confidence interval that estimates the average web browsing battery life for the iPad is ________. a) (10.35, 12.65) b) (8.55, 14.45) c) (7.47, 15.53) d) (6.32, 16.68) 23) The National Center for Education would like to estimate the proportion of students who defaulted on their student loans for the state of Arizona. The total sample size needed to construct a 95% confidence interval for the proportion of student loans in default with a margin of error equal to 4% is ________. a) 336 b) 416 c) 455 d) 601 24) As the degrees of freedom increase, the t distribution approaches the a) uniform distribution b) normal distribution c) exponential distribution d) p distribution 25) The t distribution is a family of similar probability distributions, with each individual distribution depending on a parameter known as the a) finite correction factor b) sample size c) degrees of freedom d) standard deviation 26) From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for . Which of the following statements is true? a) The standard normal distribution can be used. b) The t distribution with 50 degrees of freedom must be used. c) The t distribution with 49 degrees of freedom must be used. d) The sample size must be increased in order to develop an interval estimate. 27) A random sample of 25 employees of a local company has been measured. A 95% confidence interval estimate for the mean systolic blood pressure for all company employees is 123 to 139. Which of the following statements is valid? a) 95% of the sample of employees has a systolic blood pressure between 123 and 139. b) If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure. c) 95% of the population of employees has a systolic blood pressure between 123 and 139. d) If the sampling procedure were repeated many times, 95% of the sample means would be between 123 and 139. 28) We can use the normal distribution to make confidence interval estimates for the population proportion, p, when a) np  4 b) n(1 – p)  4 c) p has a normal distribution d) Both np  15 and n(1 – p)  15 29) Your investment executive claims that the average yearly rate of return on the stocks she recommends is at least 10.0%. You plan on taking a sample to test her claim. The correct set of hypotheses is a. H0:  < 10.0% Ha:   10.0% b. H0:   10.0% Ha:  > 10.0% c. H0:  > 10.0% Ha:   10.0% d. H0:   10.0% Ha:  < 10.0% 30) A professor would like to test the hypothesis that the average number of minutes that a student needs to complete a statistics exam is equal to 45 minutes. A Type I error would occur if the professor concludes that the average exam time is a) not equal to 45 minutes when, in reality, the average time is equal to 45 minutes. b) not equal to 45 minutes when, in reality, the average time is greater than 45 minutes. c) equal to 45 minutes when, in reality, the average time is less than 45 minutes. d) equal to 45 minutes when, in reality, the average time is not equal to 45 minutes.
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answers:1)A 11)B 21)D2)D 12)...


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