Statistics

The mean grade in this class last semester was 78.3, and the variance was 49 . The distribution of grades was unimodal and symmetrical. Using this information determine the probability that β€œJoe”, a random student you know nothing about, other than the fact that they are taking this class next semester will receive a grade that is:
Above 90
Between 85 and 95
Between 80 and 90
Lower than 65
Lower than 65 OR above 90


My question is how do you approach this question would i have to do something along these lines?

90-78.3/49?

  1. πŸ‘ 0
  2. πŸ‘Ž 0
  3. πŸ‘ 35
asked by Francisco
  1. Z = (score-mean)/SD

    SD = √variance

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions/probabilities related to the Z scores.

    Either-or probabilities are found by adding the individual probabilities.

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    2. πŸ‘Ž 0
    posted by PsyDAG

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