The shape of the distribution of the time required to get an oil change at a 10 minute oil change facility is unknown. However, records indicate that the mean time is 11.4 minutes and the standard deviation is 4.5 minutes. a) To compute the probabilities regarding the sample mean using the normal model, what size sample would be required?
b) What is the probability that a random sample of n = 35 oil changes results in a sample mean time of less than 10 minutes?
1) Choose the required sample size:
i) Sample size need to be greater than 30
ii) The normal model cannot be used if the shape of the distribution is unknown
iii) Any sample size could be used.
iv) Sample size needs to be less than 30
2) The probability is approximately . (round to 4 decimal places as needed)