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    Confidence Interval

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    Confidence interval normal probability and Hypothesis testing problems

    1) The length of time to do a complete full service oil change at Speedy-Lube, is normally distributed with a mean of 15.8 minutes and a standard deviation of 2.2 minutes. Refer to the following table. Table 5A Below normal distribution p(lower) p(upper) z x mean std.dev .0042 .9958 -2.64 10 15.8 2.2 .9719 .0281 1.91 20

    Confidence Interval for GPA of Students

    The GPA's for 10 randomly selected students are listed below. Construct a 90% confidence interval for the population standard deviation. Assume the data are normally distributed. 2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 .8 a. 1.10, 2.01 b. .32, .85 c. .53, 1.01 d. .81, 1.83

    Proportion of Students on Financial Aid

    A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. Use a 99% confidence interval to estimate the true proportion of stud

    Assume that the heights of women are normally distributed.

    Assume that the heights of women are normally distributed. A random sample of 20 women have a mean height of 62.5 inches and a standard deviation of 1.3 inches. Construct a 98% confidence interval for the population variance, (lower case sigma)2. a.(0.9,2.1) b.(0.9,4.4) c.(0.7,3.2) d.(0.9,4.2)

    Construct a 90% Confidence Interval for the Population Mean

    Construct a 90% confidence interval for the population mean. Assume the population has a normal distribution. A sample of 15 randomly selected students has a grade point average of 2.86 with a standard deviation of 0.78. a. (2.37, 3.56) b. (2.51, 3.21) c. (2.41, 3.42) d. (2.28, 3.66).

    Confidence Level Determination

    Your hospital has 500 patient - you sample 100 regarding quality of care - 74 are in favor. Data assumed to be normally distributed. Use this sample data to predict population proportion and to do so with 98% confidence (finite correction factor) a. what is the upper limit for a 99% confidence interval?

    Testing a Hypothesis and Confidence Interval

    1. The American Sugar Producers Association wants to estimate the mean yearly sugar consumption. A sample of 16 people reveals the mean yearly consumption to be 60 pounds with a standard deviation of 20 pounds. A. What is the value of the population mean? What is the best estimate of this value? B. Explain why we need to use

    Confidence Interval: Lower Bound

    A sample of 14 joint specimens of a particular type gave a same mean proportional limit stress of 8.48 MPa and sample standard deviation of 0.79 MPa. a) Calculate and interpret a 95% lower confidence bound for the true average proportional limit stress of all such joints. What, if any assumption did you make about the distri

    95% confidence interval for the mean age

    An economics professor randomly selected 100 millionaires in the United States. The average age of these millionaires was 54.8 years with a standard deviation of 7.9 years. What is the 95% confidence interval for the mean age, poplulation mean of all United States millionaires?

    Calculating a Confidence Interval

    What information is necessary to calculate a confidence interval? Is the size of the population relevant when one is determining the sample size for a confidence interval? What is necessary to determine the sample size?

    The Solution to Confidence Interval for Mean

    A sample of the math test scores of 35 fourth-graders has a mean of 82 with a standard deviation of 15. Find the 95% confidence interval of the mean math test scores of all fourth-graders. Find the 99% confidence interval of the mean math test scores of all fourth-graders. Which interval is larger? Explain why.

    Confidence Interval Estimate Between Means

    Confidence interval for Data1 & Data2. Using the following data, construct a 95% confidence level interval estimate for the difference between the mean of Data1 and Data2. Data 1 Data 2 n1= 70.0 73 X-bar = 413.5 403.7 s 38.5 30.4

    Confidence Interval for Mean GPA

    The undergraduate grade point average (GPA) for students admitted to the top graduate business schools was 3.37 (Best Graduate Schools, U.S. News and World Report, 2001). Assume this estimate was based on a sample of 120 students admitted to the top schools. Using past years Õdata, the population standard deviation can be a

    Hypothesis Claim Testing

    1. At a large publishing company, the mean age of proofreaders is 36.2 years with a standard deviation of 3.7 years. Assuming the age is normally distributed, find the following: a. If a proofreader is selected at random what is probability his/her age will be between 36 and 38 years. b. If a random selected sample 20 proofrea

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