An electrical parts manufacturer produces a specialized product targeted for a certain type of application. The analyst takes random samples of 423 from the production line. 351 were found to pass the test. a) Construct a 90% confidence interval to estimate the population proportion p. b) How large a sample is required if we want to be 90% confident that your estimate of the proportion is off by less than 4%? Data shows that the hourly wage for a production worker in a certain industry is $20. A random sample of 26 workers were selected and the standard deviation of hourly wages were found to be $1.18. Construct a 95% confidence interval to estimate the population variance of the hourly wages.