(1) What are the conditional constraints which are used to predict “RainTomorrow

Question

(1) What are the conditional constraints which are used to predict “RainTomorrow=No”?

(2) If the above conditions are satisfied, what is the probability of “RainTomorrow=No”?

(3) How do we interpret “cover=195 (76%)”? Please explain your answer in detail.

Tree as rules: Rule number: 7 RainTomorrow:Yes cover-27 (11%) prob-0.74] Pressure3pm-7.5 Rule 6 [RainTomorrow-No cover-25 (10%) prob-o.20] number: Pressure3pm-8.85 Rule 4 [RainTomorrow-No cover-195 (76%) prob=0.05] number: Pressure3pm>=1012 Cloud3pm

Explanation / Answer

(1) What are the conditional constraints which are used to predict “RainTomorrow=No”?

The conditional constraints are

1. Pressure3pm < 1012 and Sunshine >= 8.85 with prob = 0.20

2. Pressure3pm >= 1012 and Cloud3pm < 7.5 with prob = 0.05

(2) If the above conditions are satisfied, what is the probability of “RainTomorrow=No”?

So, if Pressure at 3 PM is less than 1012 and Sunshine is greater than or equal to 8.85, then the probability of no rain tomorrow = 0.2

If Pressure at 3 PM is greater than or equal to 1012 and Cloud cover at 3 pm is less than 7.5, then the probability of no rain tomorrow = 0.05

(3) How do we interpret “cover=195 (76%)”? Please explain your answer in detail.

There were 195 observations when the constraints Pressure3pm >= 1012 and Cloud3pm < 7.5 was satisfied. So, there were total 195/0.76 = 257 observations. The prob of no rain is 0.05. So out of 195 observations satisfying the constraints, number of observations for which there was no rain tomorrow = 0.05 * 195 = 10 and  number of observations for which there was rain tomorrow = 195 - 10 = 185.

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