# statistics

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All deal with a random variable X that follows a normal probability distribution with mean equal to 37 and a standard deviation of 5.

Compute P(X < 39)

Compute P(X < 29 or X > 41)

Compute P(X > 30)

Find the 42nd percentile for this distribution.

• statistics -

Z = (score-mean)/SD

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.

For last Q, Start with table (.42) and insert Z score into above equation.

• statistics -

PsyDAG, right on thanks

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