Suppose a research firm conducted a survey to determine the average amount of money steady smokers spend on cigarettes during a week. A sample of 100 steady smokers revealed that the sample mean is $20 and the sample standard deviation is $5.
Assume a steady smoker spends on average $20 with a standard deviation of $5 per week on cigarettes.
What is the probability that a sample of 100 steady smokers spend between $19.50 and $21?