Statistics Confidence Intervals, Hypothesis Testing t tables
1. You are given the following data obtained from a sample of 25 observations taken from a population that has a normal distribution. The mean is 78 and the sample standard deviation is 7. Develop a 90% confidence interval estimate for the mean of the population.
Answers
Point Estimate
Critical Value
Standard Error
Margin of Error
Confidence Interval limits:
2. A car dealership would like to estimate the mean mpg of its new model car with 95% confidence. The population is normally distributed; however, we are taking a sample of 16 cars with a sample mean of 96.52 and a sample standard deviation of 10.70. Calculate a 95% confidence interval for the population mean using this sample data.
Answers
Point Estimate
Critical Value
Standard Error
Margin of Error
Confidence Interval limits:
3. A scientist believes the concentration of radon gas in the air is greater than the safe level of 4 pci. The scientist tests the composition for 28 days and finds an average concentration of 4.4 pci with a sample standard deviation of 1 pci.
In testing the management’s belief at 0.05 level of significance, write the appropriate hypotheses:
Ho: µ<= 4 Ha:
__crit = α =
__stat = pvalue =
__crit = α =
__stat = pvalue = ___ tail
Decision:
Review for Final
Write the regression equation using the following information: 3 decimal places
SSxy = 66.8 SSxx = 9.2 ∑x = 13 ∑y = 107 n = 5
Ten percent of households in Charlestown are in foreclosure. Suppose 8 mortgage-holding households in the city were sampled. Using the Binomial Distribution tables, write all the values and their total.
What is the probability that exactly 2 of these households are in foreclosure?
What is the probability that no more than 3 households are in foreclosure?
What is the expected number of households in foreclosure?
Carefully read the paragraph
There is an 80% probability that students would finish their degree if they had assistance from advising throughout their time at school. There is a 45% probability that students will finish their degree. There is a 30% probability that students receive assistance from advising throughout their time at school.
Hints: Variables A=receiving advising, B=finishing a degree
What is the probability that students will not finish their degree?
Is there a positive influence on finishing a degree with help from advising? How do you know? Show the calculation using independent rules.
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