223 Data below show the thickness of coating of a plastic paint taken for nine samples. 20.5 21.2 18.6 20.4 19.8 17.8 23.2 22.4 20.6 Compute the standard deviation and set up a 90 per cent confidence limits for the standard deviation of the population. when the true traction bata below refer to the dividend yield from samples of corporations in electronic industry and textile industry. There is reason to believe that the population dividends are normally distributed with equal variances. Find a 95 per cent confidence interval for the population textile industry. difference in dividends and assess whether the electronic industry pays higher than the Electronics Textiles Sample size 10 Mean dividend (RS) 12 24.6 17.5 Standard deviation (RS) 5.65 3.95 12.38 /A random sample of 100 teachers in a large metropolitan area revealed a mean weekly salary of Rs 4,870, with a standard deviation of Rs 480. With what degree of confidence, can we assert that the average weekly salary of all teachers in the metropolitan area is between Rs 4,720 and Rs 5,020? entail nutlat Inet front in a cample of n = 10 12.41 The standard deviation of breaking strength of 100 cables tested by a company was 180 N. Find (a) 95%, (b) 99%, and (c) 99.73% confidence limits for the standard deviation of all cables produced by the company. 13.36 The cinema-goers were 800 people out of a sample of 1,000 persons during the period of a fortnight in a town where no TV programme was available. The cinema-goers were 700 people out of a sample of 2,800 persons during a fortnight in another town where TV programme was available. Do you think that there has been a significant decrease in propor- tion of cinema-goers after introducing TV sets? Test the hypothesis that there is no differ- ence in proportion of cinema-goers. Use a level of significance of 0.01. By applying the t-test, can it be concluded that the employees have benefited by the training? Use 5 per cent level of significance. 13.41 Samples of two different types of bulbs were tested for length of life, and the following data were obtained: Sample Size Sample Mean Sample S.D. Type 1 CO 1,234 hours 36 hours Type 2 1, 136 hours 40 hours Is the difference in means significant? normally uisuruuwu. onn mite form 3.33 Two types of batteries are tested for their length of life and the following data are obtained: Sample Size Mean Life Variance (hour) Type A 600 121 00 CO Type B 640 144 Is there a significant difference in the two means