How can i do these?

A study is to be made to estimate the proportion of residents of a certain city and its suburbs who favor the construction of a nuclear power plant near the city. How large a sample is needed if one wishes to be at least 90% confident that the estimate is within 0.12 of the true proportion of residents who favor the construction of the nuclear power plant? Click here to view page 1 of the standard normal distribution table. Click here to view page 2 of the standard normal distribution table. The sample should be people (Round up to the nearest whole number.) A random sample of 21 chocolate energy bars of a certain brand has, on average, 280 calories per bar, with a standard deviation of 15 calories Assume that the distribution of the calorie content is approximately normal. Construct a 99% confidence interval for o. Click here to view page 1 of the table of critical values of the chi-squared distribution. Click here to view page 2 of the table of critical values of the chi-squared distribution. The confidence interval is