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標題: [知識] 問數~~~高手請指點 [打印本頁]

作者: FiNaL◎峰 時間: 2013-10-31 12:26 標題: 問數~~~高手請指點

1.) A very reliable baseball player is known to get a hit when at bat 45% of the time.

He is expected to have 106 more times at bat before the end of the season, and he is 40 hits away from breaking a league hitting record.

What is the probability of him breaking that record before the end of the season?

Round your answer to 4 decimals
慳返D時間, 0.9336 同0.9332都錯

2.)
A child, (and mathematical genius!) wishes to estimate the variability in the number of candies he can collect from houses during trick-or-treating.

He randomly selects a sample of 20 houses, and records the number of candies he gets at each:

# Candies	# Houses
0 1 2 3 4	3 6 4 5 2

Find the sample variance he calculates using this data.
Round answer to 2 decimals
同樣, 1.53都係錯

作者: kaka123 時間: 2013-10-31 18:36

1.係唔係105*(0.45)^105 *105(0.55)^1+105*(0.45)^104 *105(0.55)^2+.....+105*(0.45)^40 *105(0.55)^65

作者: FiNaL◎峰 時間: 2013-10-31 23:35

引用:

原帖由 kaka123 於 2013-10-31 18:36 發表
1.係唔係105*(0.45)^105 *105(0.55)^1+105*(0.45)^104 *105(0.55)^2+.....+105*(0.45)^40 *105(0.55)^65

'[修正] 今朝未訓醒未讀清你條formula

應該係 106C40 *0.45^40*0.55^66 + 106C41 * 0.45^41*0.55^65+....+106C106*0.45^0*0.55^106
但係咁計通常會用z score table/ excel計
我唔知我邊到計錯/...\

[ 本帖最後由 FiNaL◎峰於 2013-11-1 04:56 編輯 ]

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