SOLUTION: Q1) The diameter of a wheel from a certain plant may be considered to be normally distributed with variance 4 cm^2. 1.1) If a sample of 20 wheels has a mean of 45 cm, give a 95

Question 796717: Q1) The diameter of a wheel from a certain plant may be considered to be normally distributed with variance 4 cm^2.
1.1)
If a sample of 20 wheels has a mean of 45 cm, give a 95% Confidence Interval for the mean diameter of the wheels from the factory.
Enter your answer as an interval [ a, b ] where a, b should be accurate to two decimal places.

1.2)
If an interval of width (at most) 0.1cm is to contain the mean with a confidence of 90%, how large should the sample size be?
Give your answer as the smallest whole number which would ensure the interval is no wider than 0.1cm
Q2)
On 30 weekdays an average of 100 cars turned right at a busy intersection, with a standard deviation of 7.5. Give a 95% confidence interval for the number of cars turning right on average at this intersection on a typical weekday.
Enter your answer as an interval [ a, b ] where a, b should be accurate to two decimal places.

Thanks in advance, I have no clue how to solve any of them..
Answer by psbhowmick(878) (Show Source): You can put this solution on YOUR website!
If you need help with these Stat problems then send me an email.
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