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a) Average total daily sales at a small food store are known to be $451.75. The store manager recently made some changes in displays of goods, order within aisles, and other changes, and she now wants to know whether average sales volume has increased. A random sample of 14 days shows Xbar = $502.95 and s = $64.00. You can assume normality. Using alpha = 4%, is the sampling result significant? Explain.
(b) A simple random sample of 350 households from a large community was selected to estimate the mean residential electricity usage per household during January of last year. Another simple random sample of 420 households was selected, independently of the first, to estimate mean residential electricity usage during January of this year. The sample results (expressed in kilowatt hours) were:
Last Year Sample size 350 Sample mean 1272 kwh Sample sd 259 kwh
This Year Sample size 420 Sample mean 1335 kwh sample sd 265 kwh
You feel that the mean usage of electricity has increased for January of this year compared to January of last year. Carry out the appropriate hypothesis test at 5%.
How would you use the binomial distribution in making a business decision during a normal day of work in the career of your choice?
Use the critical values for z of 1.65 and a p level of approximately 0.10, or 10%. For each of the following values, determine if you would reject or fail to reject the null hypothesis:
What is an independent sample? What is a related sample? When should researchers use different hypothesis tests for independent and related samples?
Using alpha = 0.05 and a computed value of +4.49, can we conclude that the percentage of claims for married policyholders is less then for single policyholders?
Carry out t test and find out whether or not demand and unit price are related. Let a=.05. Carry out an F test and find out whether or not demand and unit price are related.
etting the significance level at a very high cutoff (such as 15%) increases chances of what type of error? Why do Type II errors concern scientists? Why have confidence levels of significance been set at 5% and 1%?
Let z represent the standard normal variable and suppose a value is randomly selected. Find each of the following probabilities by:
Based on these data, does it seem that strength of relationship between sales and promotions expenditures is enough to permit using linear regression forecasting model? Describe why?
What conclusions can you draw about the nature of the relationship between anxiety and exam performance?
To avoid the problem of not having access to Tables of F distribution with values given for the lower tail, the numerator of the test statistic should be the one with:
A random sample obtained from a population has a mean of µ=100 and a standard deviation of σ = 20. The error between the sample mean and the population mean for a sample of n = 16 is 5 points and the error between a sample men and population mean ..
They plan to set up a radar trap and check the speeds of 80 randomly selected cars. Can this distribution be approximated by a normal curve?
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