L' Reflection Direction: Find the interval estimate of the following problem. 1. A random sample of 70 Grade 1 1 students at Lorma Colleges showed a mean monthly Allowance of Php. 3500,00 with a population standard deviation of Php. 100.00. On the assumption that the monthly allowance of the students is normally distributed. a Construct a 90%% confidence interval for the mean monthly allowance. b. Construct 95% confidence interval for the mean monthly allowance. 2. An electrical firm manufactures light bulbs for LCD projectors with life spans that are approximately normally distributed. A randomly selected sample of 25 light bulbs have a mean life span of 600 hours with a standard deviation of 50 hours. a Find 95% confidence interval for the population mean of all the light bulbs produced by the electrical firm? b. Find 99% confidence interval for the population mean of all the light bulbs produced by the electrical firm? 3. A marketing researcher randomly selects 20 female students in a certain university and found out that their average monthly expenditures for their cellphone loads is Php. 500.00 with a standard deviation of Php. 75.00. Find the 90% confidence interval for the average expenditures of female students for their cell phone loads