Help me solve 9, 10 and 11

9. A light bulb is drawn at random from the large supply with average life of 900 hours and o = 60 hours. Find the probability that it will last more than 920 hours Find the probability that 36 bulbs sample average is more than 920 hours 10 (SLO). In a random sample of size 200, the average Cholesterol level of group of adults is 40.015 If the standard deviation in the city's adult population is 6.12 find 95% confidence interval for L 11. A researcher tries to estimate the population mean by using sufficiently large sample. The probability is 95 that the sample mean X will not differ from the true mean O by more than 5% of standard deviation. How large a sample should be taken? RT 0.05 0.95 cv+ = inVT( O is v = 41. 1, while the sample standard deviation is s = 3.1