One tailed test of means• A hospital uses large quantities of packaged doses of a particular drug. The individual dose of this drug is 100cc. The action of this drug is such that the body will harmlessly pass off excessive doses. On the other hand insufficient doses do not produce the desired result. The hospital has purchased this drug from the same manufacturer for the last 2 yrs and knows that the population s.d. is 2 cc. The hospital inspects 50 doses of this drug from a very large shipment and finds the mean of these doses to be 99.75 cc. If the hospital sets a 0.10 significance level, should the shipment be accepted?
• Hinton press hypothesizes that the average life of its largest web press is 14500 hrs. They know that the s.d. of press life is 2100 hrs. From a sample of 25 presses, they find a sample mean of 13000 hrs. At a .01 significance level, should the company conclude that the average life of the presses is less than 14500 hrs?
Two tailed tests of proportions-large samples• A company is evaluating the proportion of the employees who are promotable to the next level. The HR director tells the president that approx. 80% of the employees in the company are promotable. An evaluation committee does an in-depth interview of 150 employees and concludes only 70% of the employees in the sample are promotable. The president wants to test at a significance level of 0.05 the hypothesis that 0.8 of the employees are promotable.
• A personnel specialist is recruiting a large number of specialists for an overseas assignment. During the testing process, when asked how things were progressing, she said “ I think the average score will be around 90”. When management reviews 20 of the tests compiled, it finds that the mean score is 84 with a s.d. of 11. If management wants to test her hypothesis at 0.10 level of significance what should it do?
Hypothesis testing-differences between means and proportions• Sampling distribution of difference between means• Mean of Sampling distribution of difference between means• Standard error of difference between 2 means
• A manpower development statistician is asked to determine whether the hourly wages of workers are the same in 2 cities. The data are in the attached table. The company wants to test at 0.05 level whether there is no difference between the wages for workers in the two cities.
Hourly S.D . Of sample Size of sample earnings from sampleCity 1 8.95 0.40 200City 2 9.10 0.60 175
Differences between means- dependant samples• A health spa has advertised a weight reducing program and claims that the average participant will lose more than 17 pounds. A somewhat overweight executive is interested in the program, but wants some hard evidence. The spa allows him to select 10 participants at random and record their weights before and after the program.The overweight exec wants to test at 5% level of significance the claimed average weight loss of more than 17 pounds.
Tests for differences in proportions: large sample sizes• Standard error of the difference between proportions
• A pharma company wants to test 2 new compounds intended to reduce blood pressure levels. The compounds are administered to two different sets of laboratory animals. In group 1, 71 out of 100 animals tested responded positively to drug-1. In group 2, 58 out of 90 animals tested responded positively to drug 2. The company wants to test at .05 level whether there is a difference between the efficacies of the two drugs
Case presentations• Next week: Care Hygiene• Hindustan Foods