# Assignment

Z and t test Problems

A manufacturer of sports equipment has develop new synthetic fishing line that he claims has men breaking strength of 8 kg with standard deviation of 0.5 kg . Test the hypothesis µ = 8 kg against alternative µ ? 8 kg if a random sample of 50 lines is tested and found mean breaking strength of 7.8 kg Use 0.01 level of significance.

An electrical firm manufactures light bulbs that have length of life that is approximately normally distributed with a mean 1600 hours and standard deviation of 80 hours. Test the hypothesis that µ =1600 hours against the alternative µ ? 1600 hours if a random sample of 30 bulbs has average life 1576 hours. Use a 0.01 level of significance.

An instructor gives his class an examination which as he knows from years of experience yield = 78 and = 7 . His present class of 22 obtains a mean of 82 . Is he correct in assuming that this is an superior class use 0.05 level of significance.

A machine is set to fill baby milk in boxes with mean weight 0f 500 grams per box. The standard deviation is known to be 176.8 grams A random sample of 50 filled boxes shows mean weight of milk of 540 gm. Is there any reason to believe that machine is over filling use = 0.05

The strength of steel wire made by an existing process is normally distributed with mean 2500 and standard deviation300 A batch of wire made by a new process and a sample of 25 measurements gives an average strength 2640. Has engineer strong evidence to justify changing to a new process at = 0.05

A plant is in control when the average quantity of instant coffee that is packed in a jar is 6 ounces. The standard deviation of quantity is 0.2 ounce. A sample of 100 jar is selected at random and average quantity is found to be 6.1 ounces Is the process out of control = 0.05

The average height of females in the freshman class of a certain college has been 162.5 cm with standard deviation 6.9 cm. Is there reason to believe that there has been change in average…