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A discrete probability distribution function has two characteristics:
A child psychologist is interested in the number of times a newborn baby's crying wakes its mother after midnight. For a random sample of 50 mothers, the following information was obtained. Let X = the number of times a newborn wakes its mother after midnight. For this example, x = 0, 1, 2, 3, 4, 5.
P(x) = probability that X takes on a value x .
x | P(x) |
0 | P(x=0)=250 |
1 | P(x=1)=1150 |
2 | P(x=2)=2350 |
3 | P(x=3)=950 |
4 | P(x=4)=450 |
5 | P(x=5)=150 |
X takes on the values 0, 1, 2, 3, 4, 5. This is a discrete PDF because
Suppose Nancy has classes 3 days a week. She attends classes 3 days a week 80% of the time, 2 days 15% of the time, 1 day 4% of the time, and no days 1% of the time. Suppose one week is randomly selected.
Let X = the number of days Nancy ____________________ .
Let X = the number of days Nancy attends class per week .
Suppose one week is randomly chosen. Construct a probability distribution table (called a PDF table) like the one in the previous example. The table should have two columns labeled x and P(x) . What does the P(x) column sum to?
x | P(x) |
0 | 0.01 |
1 | 0.04 |
2 | 0.15 |
3 | 0.80 |
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