z-table

  1. C

    Finding Probability using z-table help

    The question is... Assume that the readings at freezing on a batch of thermometers are normally distributed with a mean of 0°C and a standard deviation of 1.00°C. A single thermometer is randomly selected and tested. Find the probability of obtaining a reading less than -0.976°C. P(Z<-0.976)=...
  2. P

    The z-scores of the 68-95-99.7 rule aren't matching up with the values in my z-table

    The z-scores from the 68-95-99.7 rule, which are 1, 1.96 (or 2), and 3 according to my textbook, arent matching up with the values i get if i try to find them using the Z-table in the appendix of the textbook. For example, the rule says 95% of the normal distribution falls within 1.96-2 std...
  3. C

    This is probably easy for you but very hard for me!

    Can someone please help me figure out how to do this problem? A professor knows that from past experience that the time for students to complete a quiz has an N(19, 3) distribution. a. If he allows 20 minutes for the quiz, what percent of the students will not complete the quiz? b...
  4. M

    need help to calculate variance of sales

    Hi, I'm trying to calculate numerical value of the variance of sales, and the probability of a sale greater than 6300 cans. but it seems wrong because I get very very large numbers. we are given that SALES = 40710 - 430P where sales are cans sold per week. and PRICE ~N(75,25) I...