Statistics and Probability Answers

Suppose the mean number of days to germination of a variety of seeds is 22, with a standard deviation of 2.3 days. Find the probability that the mean germination time of a sample of 160 seeds will be within 0.5 days of the population mean.

3 suppose ‘X’ is normally distributed with mean 20 and variance 8 i.e X-NID

Find

A P(25≤X≤30)

B P(X≥25)

4 Given the following discrete probability destruction.

X 1 5 7 9

F(x) 1/6 2/6 2/6 1/6

Find

A the expected value of x E(X)

The variance of x V(X)

6 the probabilities that Abebe passes microeconomics is 2/3 and the probability that he passed statics 4/9. If the probability of passing both courses is 1/4 ,what is the probability that Abebe will pass at lease one of these courses

How many two-digits numbers can be made from the digits 6,7 and 8 if repetition of the digits is allowed

The manager of the machine-made kretek kretek cigarette company RAENAK found that 12% of its production was below production standards (poor). One day, the manager received a report that on that day 17% of substandard cigarette products were obtained from a random sample of 1000 cigarettes. Test whether the manufacturing defects (17%) are random or permanent (machines need to be repaired)! Use a= 0.05!

Manajer perusahaan rokok RAENAK sigaret kretek mesin mendapati bahwa 12% dari produksinya berada di bawah standar produksi (buruk). Pada suatu hari, manajer tersebut mendapatkan laporan bahwa pada hari tersebut didapatkan produk rokok di bawah standar sebesar 17% dari sampel acak sebesar 1000 batang rokok. Ujilah apakah cacat produksi (sebesar 17%) tersebut bersifat random atau permanen (mesin harus diperbaiki)! Gunakan a= 0,05! The manager of the machine-made kretek kretek cigarette company RAENAK found that 12% of its production was below production standards (poor). One day, the manager received a report that on that day 17% of substandard cigarette products were obtained from a random sample of 1000 cigarettes. Test whether the manufacturing defects (17%) are random or permanent (machines must be repaired)! Use a=0.05!

A company manufactures a new type of mosquito repellents with the period of effectiveness that is approximately normally distributed with a standard deviation of 30 hours. A sample of 40 repellents was taken and the average period of effectiveness is 290 hours. Calculate a 96% confidence interval for the true mean of the period of effectiveness

It is claimed that the average weight of a bag of biscuits is 250 grams with a standard deviation of 20.5 grams. Would you agree to this claim if a random sample of 30 bags of biscuits showed an average weight of 240 grams, What is the tabular value if the level of significance is 5%?

City planners wish to estimate the mean lifetime of the most commonly planted trees in urban settings. A sample of 16 recently felled trees yielded mean age 32.7 years with standard deviation 3.1 years. Assuming the lifetimes of all such trees are normally distributed, construct a 99.8% confidence interval for the mean lifetime of all such trees.

A random sample is drawn from a normally distributed population of known standard deviation 5. Construct a 99.8% confidence interval for the population mean based on the information given (not all of the information given need be used).

a. n = 16, 𝑥̅= 98, 𝑠 = 5.6

b. n = 9, 𝑥̅= 98, 𝑠 = 5.6

A government agency was charged by the legislature with estimating the length of time it takes citizens to fill out various forms. Two hundred randomly selected adults were timed as they filled out a particular form. The times required had mean 12.8 minutes with standard deviation 1.7 minutes. Construct a 90% confidence interval for the mean time taken for all adults to fill out this form.