218) A brokerage firm needs information concerning the standard deviation

Question : 218) A brokerage firm needs information concerning the standard deviation : 1416812



218) A brokerage firm needs information concerning the standard deviation of the account balances of its customers. From previous information it was assumed to be $250. A random sample of 61 accounts was checked. The standard deviation was $286.20. At α = 0.01, test the firm's assumption. Assume that the account balances are normally distributed.




219) In one area, monthly incomes of technology related workers have a standard deviation of $650. It is believed that the standard deviation of monthly incomes of non-technology workers is higher. A sample of 71 non-technology workers are randomly selected and found to have a standard deviation of $950. Test the claim that non-technology workers have a higher standard deviation. Use α = 0.05.




220) A statistics professor at an all-men's college determined that the standard deviation of men's heights is 2.5 inches. The professor then randomly selected 41 female students from a nearby all-female college and found the standard deviation to be 2.9 inches. Test the professor's claim that the standard deviation of female heights is greater than 2.5 inches. Use α = 0.01.




221) A new gun-like apparatus has been devised to replace the needle in administering vaccines. The apparatus, which is connected to a large supply of vaccine, can be set to inject different amounts of the serum, but the variance in the amount of serum injected to a given person must not be greater than 0.08 to ensure proper inoculation. A random sample of 25 injections was measured. Suppose the P-value for the test is State the proper conclusion using




Provide an appropriate response.

222) In 2010, 36% of adults in a certain country were morbidly obese.  A health practitioner suspects that the percent has changed since then. She obtains a random sample of 1042 adults and finds that 393 are morbidly obese.  Is this sufficient evidence to support the practitioner's claim at the α = 0.1 level of significance? Round to five decimal places when calculating the test statistic.







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