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Confidence Interval

Confidence Intervals and Hypothesis Testing

Please help with the following problem. Provide step by step calculations in Excel. 17. Consider a 98% confidence interval to estimate a population mean based on a sample of 625 observations with a sample mean of 425 and a sample standard deviation of 150. How many units wide would such a confidence interval be? 18. In a

Interpreting Results

Refer to the accompanying Minitab display of a 95% confidence interval generated using the methods of this section. The sample display results from using a random sample of speeds of drivers ticketed on a section of Interstate 95 in Connecticut. Variable N Mean StDev SE Mean 95% CI Speed

Minimum Sample Required in Statistics

1.) With a margin of error of 0.050; confidence level of 99% ^p and ^q unknown, what is the minimum sample size required to estimate a population proportion or percentage? 2.) Amounts lost by gamblers who took a bus to Atlantic City casino: 99% confidence; n=40, mean of values in sample = $189,standard deviation is known to b

Calculating Confidence Intervals

1. A study was conducted to estimate the mean amount spent on birthday gifts for a typical family having two children. A sample of 150 was taken, and the mean amount spent was $225. Assuming a standard deviation equal to $50, find the 95% confidence interval for mu, the mean for all such families. 2. A 95% confidence interv

Confidence Intervals with Household Income

If 400 households have an annual average income of $50,000 with a standard deviation of $4,000, what is the 90% confidence interval that includes the population household income? Please show all steps of the work, so tht I can understand the formulas/process.

True or False Questions about Statistics: If in a probability distribution you got the sum of probabilities less than one, it may mean that you skipped some possible outcome/outcomes.

TRUE OR FALSE (With justification)? If in a probability distribution you got the sum of probabilities less than one, it may mean that you skipped some possible outcome/outcomes. Health insurance policies are set up in such a way that a healthy person has a negative expected value, and a sickly person has a positive one.

Confidence interval estimate of the population total value

Please help with the following problem. A stationery store wants to estimate the total retail value of the 300 greeting cards that it has in its inventory. What are the upper and lower limits of the 95% confidence interval estimate of the population total value of all greeting cards that are in inventory if a random sample o

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 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

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

Dental Plan as part of the Benefits Package; one family Per yer, Sample of 45

The Human Relations Department of Electronics, Inc., would like to include a dental plan as part of the benefits package. The question is: How much does a typical employee and his or her family spend per year on dental expenses? A sample of 45 employees reveals the mean amount spent last year was $1,820, with a standard deviatio