Question 11A standard flammability test for fabric is to place a standard-sized piece of fabric under a flame fora fixed period of time, and then measure the length of the charred portion of fabric. Suppose the procedure is carried out using a sample of 64 such portions of fabric and the average length of charred portions of fabric was 3cm with a variance of 0.16cm2. Construct a 90% confidence interval for the average length of charred portions of this fabric and give the lower limit.
2.96712.91783.08253.0329None of the above

Question 12A telephone company’s records indicate that private customers pay on average R17.10 per month for long distance calls. A random sample of 10 customers’ accounts during the given month produced a sample mean of R22.10 expended for long distance calls and a sample variance of R45. A 5% significance test is to be performed to determine if the mean level of billing for long distance calls per month is more than R17.10. The null and alternative hypotheses are respectively:H0:µ = 17.10; H1µ<17.10H0:µ = 22.10; H1: µ > 22.10H0:µ = 17.10; H1:µ > 17.10H0:µ = 17.10; H1µ
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Question 13As part of a study on plant growth, a plant physiologist grew 8 individually potted soya bean seedlings of the type called “Wells II.” She raised the plants in a greenhouse under identical environmental conditions (light, temperature, soil and so on). She measured the total stem length(in cm) for each plant after 16 days of growth. The results are as follows:

A point estimate for the mean stem length of “Wells II” soya bean seedlings on day 16 of growth (accurate to 4 decimal places) is: ______169.2
Question 14From a sample of 100 Bloemfontein car commuters, the sample mean time to commute to work daily was found to be 35.8 minutes. It is known that the population standard deviation is 20 minutes. Find the margin of error with a 95% confidence level.
3.1.9623.29
Question 15The mean mass of 50 male students who showed above average participation in athletics was 68 kg with a standard deviation of 3 kg, while 40 male students who showed no interest in such