The frequency of the score in [90, 100] is 0.08, so there are two people in [90, 100]. In addition, when the number of people with grades between [60,70] is 7, the frequency is 0.28, and when the number of people with grades between [70,80] is 65,438+00, the frequency is 0.4. There are 2 people in [90, 100], so there are 25-2 1 = 4 people with scores between [80, 90], and the frequency is 0. 16.
So the estimated median is 0.08 * 55+0.28 * 65+0.4 * 75+0.16 * 85+0.08 * 95 = 73.8.
The estimated median value is 73.8.
2。 There are 4 people in [80,90] and 2 people in [90,0/00]. Then choose any person from them, and the result will be a combination of (2,6) =15 results. It happens that someone's score is [90, 100], so the result of this event is combination (1 4) * combination (1 2) = 8, so the probability of this event is 8/ 15.