(c) A research company wants to estimate the percentage of citizens of a city who are willing to invest in real estate in the coming 2 years. and will declare that the real estate market is shrinking if this percentage is lower than 12%. In a survey among 1400 citizens, 157 of them are willing to invest within 2 years. Construct a 90% confidence interval for the proportion of the citizens of that city who are willing to invest in real estate in the coming 2 years and briefly comment on the real estate market. 0 The proportion is [give an answer between 0 and 1 correct to 4 decimal places]. The critical value is [correct to 4 decimal places]. According to the formula [select one below] On = (z/e)2/4 Op i 2W 05: :l: ts/ On = P(1 - 10)(Z/e)2 On = (za/e)2 05: :l: za/ the confidence interval is: E 11' 3 According to the confidence interval, although the 6 is 3 than [give an answer between 0 and 1 here], the research company % condent that the of citizens who are willing to invest in real estate in the coming 2 years is truly . Therefore, the research company declare that the real estate market in this city is shrinking (d) The manager of a singing agency wants to know the customer spending on CD on their singers. It is believed that it is a good result if customers would spend at least an average of $1100. A random sample of 18 customers is selected. The spending data on CD (in dollars) are listed below: 1343 1460 1399 951 1498 1807 1597 1304 1056 1365 1118 1050 963 1510 1384 1220 1764 928 Use the given data to construct a 98% confidence interval estimate of the mean spending on CD on their singers and briefly comment and suggest on the spending of the customers on the singers. The mean and standard deviation of the data are and respectively [correct to 4 decimal places]. The critical value is [correct to 4 decimal places]. According to the formula [select one below] On = p(1 p)(z/e)2 OP in NW p) On : (z/e)2/4 052 d: za/ 03': d: ts/ On = (20/9)2 the confidence interval is: g p, S According to the confidence interval, the manager is % confident that the spending is than . Therefore, the mean spending of customers the expectation of the company and the singing agency think of more promotion on their singers in selling CD