[問題] 最佳樣本數估計母體平均
題目如下：
Dylan Jones kept careful records of the fuel efficiency of his new car.
After the first nine times the filled up the tank,hefound the mean was 23.4
miles per gallon with a sample standard deviation of 0.9 mpg.
（1）：在95％信心水準下，求解信賴區間？
第一小題沒有問題
23.4＋2.306*(0.9/√9)=24.092
23.4-2.306*(0.9/√9)=22.708
α/2=0.025 T(8)=2.306
（2）:How many times should the fill his gas tank to obtain a margin of
error below 0.1 mpg?
解答算法：(2.306*0.9/0.1)^0.5=431
自己算法：(1.96*0.9/0.1)^0.5=312
關鍵問題在於解答帶Ｔ值,而我是帶入常態值
所以到底哪一個是正確的答案,請多多指教,謝謝.
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