急 ! F5 about Dispersion 11q1

Bid

2013-03-14 1:57 am

請詳細步驟教我計以下三條 :

13) It is given that the mean mark of thescores in the Listening test in Chinese and English are 70 and 56.8respectively, while the standard deviations are 15 and 4.5 respectively. If Mayperforms equally well in both Listening tests and her score in the ChineseListening test is 79. find her score in English Listening test.

14) The scores of Lily and Elaine in an IQTest are 48 and 66 respectively, and their standard scores are 0.1 and 1.3respectively. Find the mean and the standard deviation of the marks in the IQTest.

15) In a computer games contest, thestandard scores of Chi Kit and Chi Lok are 0.8 and -2.4 respectively. If theirmarks are 235 and 131 respectively, find the mean and the standard deviation ofthe marks in the contest.

回答 (1)

用戶9112

2013-03-15 4:07 am

✔ 最佳答案

(13) Standard score of Chinese Listening test = (79 – 70)/15 = 0.6Let the score of the English Listening test be xStandard score of English Listening test = 0.6 = (x – 56.8)/4.5x = 56.8 + 4.5 × 0.6 = 59.5 (14) Let the mean and standard deviation be μ and σ respectively(48 – μ)/σ = 0.1 ⟹ 48 – μ = 0.1σ…(1)(66 – μ)/σ = 1.3 ⟹ 66 – μ = 1.3σ…(2)(2) – (1) ⟹ 18 = 1.2σ ⟹ σ = 15Sub into (1) 48 – μ = 1.5 ⟹ μ = 46.5 (15) Let the mean and standard deviation be μ and σ respectively(235 – μ)/σ = 0.8 ⟹ 235 – μ = 0.8σ…(1)(131 – μ)/σ = -2.4 ⟹ 131 – μ = -2.4σ…(2)(1) – (2) ⟹ 104 = 3.2σ ⟹ σ = 32.5Sub into (1) 235 – μ = 0.8 × 32.5 ⟹ μ = 209

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