# An Example of {AND, OR, Given that} Using a Normal Distribution

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An Example of {AND, OR, Given that} Using a Normal Distribution
By Henry Mesa

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy.

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less.

No, they share the common days 266 to 282.
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 1. Are events A and B disjoint? No, they share the common days 266 to 282.

Yes, they do not share any common days.
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 2. Are events B and C disjoint? Yes, they do not share any common days.

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 3. Calculate P(B OR C) P(X < 234 OR 250 < X < 282) = = P(Z < -2) + P( -1< Z< 0 ) = = Using rule

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 3. Calculate P(B OR C) P(X < 234 OR 250 < X < 282) = = P(Z < -2) + P( -1< Z< 0 ) = =

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 4. Calculate P(A OR B) P(250 < X < 282 OR 266 < X < 298) = P(250 < X < 298) = P( -1 < Z < 2 ) = = 0.815Using 68 – rule

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 4. Calculate P(A OR B) P(P(250 < X < 282 OR 266 < X < 298) = P(250 < X < 298) = P( -1 < Z < 2 ) = =

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 5. Calculate P(A AND B) P(250 < X < 282 AND 266 < X < 298) = P(266 < X < 282) = P(0 < Z < 1) = Using rule. =

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 5. Calculate P(A AND B) P(250 < X < 282 AND 266 < X < 298) = P(266 < X < 282) = P(0 < Z < 1) =

There is no chance that one observation can meet both criteria.
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. 6. Calculate P(B AND C) P(X < 234 AND 250 < X < 282) = There is no chance that one observation can meet both criteria.

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. The new whole/sample space. 7. Calculate P(A | B) = 0.5 Given that the pregnancy lasted between 250 and 282 days, there is a 50 % chance that this particular pregnancy lasted between 266 and 298 days.

Consider the following problem
Consider the following problem. The length of human pregnancy in days, has an average of 266 days, and a standard deviation of 16 days. The distribution is normal. Let the random variable X denote the length of a human pregnancy. Let event A be a pregnancy lasts between 266 days and 298 days. Let event B be a pregnancy lasts between 250 days 282 days. Let event C be a pregnancy lasts 234 days or less. The new whole/sample space. 8. Calculate P(B | A) = Given that the pregnancy lasted between 266 and 298 days, there is a % chance that this particular pregnancy lasted between 250 and 282 days.

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