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Probability in Random Selection

I thought I understood this, but my instructor advised me my answers were wrong. I have not heard back in three days from him and I need to understand this. Please help me. If the table below is not acceptable, please let me know and I will make it in a word document and attach. Thank you.

An allergy drug is tested by giving 120 people the drug and 100 people a placebo. A control group consists of 80 people who were given no treatment. The number of people in each group who showed improvement appears in the table below.

..................................allergy drug...............placebo.........control..........Total
Improvement............65.................................42.................31................138

No improvement.......55................................58.................49..................162

Total........................120.............................100.................80................300

1) What is the probability that a randomly selected person in the study was given either the drug or the placebo?

2) What is the probability that a randomly selected person either improved or did not improve?

3) What is the probability that a randomly selected person either was given the drug or improved?

4) What is the probability that a randomly selected person was given the drug and improved?

Solution Summary

The probability in random selection is examined.

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