1. A random sample of six steel beams has mean compressive strength of 58.392 psi (pounds per square inch) with a standard deviation of s - 648 psi. Test the null hypothesis H,-H - 58,000 psi against the alternative hypothesis H; 4 > 58,000 psi at 5% level of significance (value for t at 5 degree of freedom and 5% significance level is 2.0157). Here i denotes the population mean (AMIE, Summer 2000)

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OMANTEL I.
Done T TEST EXERCISE_c4bf49f49d24...
1 من 3
EXERCISE
1.
A random sample of six steel beams has mean compressive strength of 58.392 psi (pounds per
square inch) with a standard deviation of s - 648 psi. Test the null hypothesis
H =u = 58,000 psi against the alternative hypothesis H,: H> 58,000 psi at 5% level of significance
(value for t at 5 degree of freedom and 5% significance level is 2.0157). Here u denotes the population
mean.
(A.MIE., Summer 2000)
2. A certain cubical the was thrown 96 times and shows 2 upwards 184 times. Is the the biased?
Ans. die is biased.
3. In a sample of 100 residents of a colony 60 are found to be wheat eaters and 40 rice caters. Can we
assume that both food articles are equally popular?
4. Out of 400 children, 150 are found to be under weight. Assuming the conditions of simple sampling,
estimate the percentage of children who are underweight in, and assign limits within which the
per-centage probably lies.
Ans. 37.5% approx. Limits - 37.5 + 3 (2.4)
5. 500 eggs are taken at random from a large consignment, and 50 are found to be bad. Estimate the
percentage of bad eggs in the consignment and assign limits within which the percentage probably lies.
Ans. 10%, 10 3.9
6.
A machine puts out 16 imprefect articles in a sample of 500. After the machine is repaired, puts out
3 imprefect articles in a batch of 100. Has the machine been improved?
Ans. The machine has not been improved.
7. In a city A, 20% of a random sample of 900 school boys had a certain slight physical defect. In
another city B, 18.5% of a random sample of 1600 school boys had the same defect. Is the difference
between the proportions significant?
Ans. z = 0.37, Difference between proportions is significant.
8. In two large populations there are 30% and 25% respectively of fair haired people. Is this difference
likely to be hidden in samples of 1200 and 900 respectively from the two populations?
Ans. z - 2.5, not hidden at 5% level of significance.
9.
One thousand articles from a factory are examined and found to be three percent defective. Fifteen
hundred similar articles from a second factory are found to be only 2 percent defective. Can it reasonably be
concluded that the product of the first factory is inferior to the second?
Ans. It cannot be reasonable concluded that the product of
the first factory is inferior to that of the second.
10. A manufacturing company claims 90% assurance that the capacitors manufactured by them will
show a tolerance of better than 5%. The capacitors are packaged and sold in lots of 10. Show that
about 26% of his customers ought to complain that capacitors do not reach the specified standard.
Table 2: Critical Values of Student's t-Distribution
Level of significance for two-tailed test
df
0.20
0.10
0.05
0.02
0.01
df
Level of significance for one-tailed test
0.10
0.05
0.025
0.01
0.005
1
3.078
6314
12.706
31.821
63.657
1
1.886
2.920
4.303
6.965
9.925
110
Transcribed Image Text:OMANTEL I. Done T TEST EXERCISE_c4bf49f49d24... 1 من 3 EXERCISE 1. A random sample of six steel beams has mean compressive strength of 58.392 psi (pounds per square inch) with a standard deviation of s - 648 psi. Test the null hypothesis H =u = 58,000 psi against the alternative hypothesis H,: H> 58,000 psi at 5% level of significance (value for t at 5 degree of freedom and 5% significance level is 2.0157). Here u denotes the population mean. (A.MIE., Summer 2000) 2. A certain cubical the was thrown 96 times and shows 2 upwards 184 times. Is the the biased? Ans. die is biased. 3. In a sample of 100 residents of a colony 60 are found to be wheat eaters and 40 rice caters. Can we assume that both food articles are equally popular? 4. Out of 400 children, 150 are found to be under weight. Assuming the conditions of simple sampling, estimate the percentage of children who are underweight in, and assign limits within which the per-centage probably lies. Ans. 37.5% approx. Limits - 37.5 + 3 (2.4) 5. 500 eggs are taken at random from a large consignment, and 50 are found to be bad. Estimate the percentage of bad eggs in the consignment and assign limits within which the percentage probably lies. Ans. 10%, 10 3.9 6. A machine puts out 16 imprefect articles in a sample of 500. After the machine is repaired, puts out 3 imprefect articles in a batch of 100. Has the machine been improved? Ans. The machine has not been improved. 7. In a city A, 20% of a random sample of 900 school boys had a certain slight physical defect. In another city B, 18.5% of a random sample of 1600 school boys had the same defect. Is the difference between the proportions significant? Ans. z = 0.37, Difference between proportions is significant. 8. In two large populations there are 30% and 25% respectively of fair haired people. Is this difference likely to be hidden in samples of 1200 and 900 respectively from the two populations? Ans. z - 2.5, not hidden at 5% level of significance. 9. One thousand articles from a factory are examined and found to be three percent defective. Fifteen hundred similar articles from a second factory are found to be only 2 percent defective. Can it reasonably be concluded that the product of the first factory is inferior to the second? Ans. It cannot be reasonable concluded that the product of the first factory is inferior to that of the second. 10. A manufacturing company claims 90% assurance that the capacitors manufactured by them will show a tolerance of better than 5%. The capacitors are packaged and sold in lots of 10. Show that about 26% of his customers ought to complain that capacitors do not reach the specified standard. Table 2: Critical Values of Student's t-Distribution Level of significance for two-tailed test df 0.20 0.10 0.05 0.02 0.01 df Level of significance for one-tailed test 0.10 0.05 0.025 0.01 0.005 1 3.078 6314 12.706 31.821 63.657 1 1.886 2.920 4.303 6.965 9.925 110
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