algebra/math

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The breaking strength (in pounds) of a certain new synthetic is normally distributed, with a mean of 169 and a variance of 9. The material is considered defective if the breaking strength is less than 163 pounds. What is the probability that a single, randomly selected piece of material will be defective? (Give the answer to two decimal places.)

  • algebra/math -

    I am not certain if you use the standard notation that variance = (standard deviation)^2
    if so , then SD = 3

    I make use of this webpage for routine standard deviation problems
    http://davidmlane.com/hyperstat/z_table.html

    enter the mean of 169 and sd of 3, then click the "below" button and enter 163

    I got a probability of.002275

    If you meant your sd to be 9, make the necessary changes in your input

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