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数学 高校生

数Bの統計分野です。 標本平均の平均が母平均に等しくなる理屈は理解しているのですが、この(2)において、標本平均を母平均と同じになるとしているように感じたのですが、どういうことか解説お願いします。

例題 342 標本平均の平均・ 標準偏差 ☆☆☆ (1)ある高校の男子の体重の平均は62kg,標準偏差は9kg である。この 高校の男子 100 人を無作為に選ぶとき,この100 人の体重の平均 X の平 均と標準偏差を求めよ。 1 2 (2)ある母集団から復元抽出された大きさ3の標本の変量が X1, X2, X であるとき、標本平均 X の平均と標準偏差 を求めよ。ただし,X1の確率分布は,右の表 の通りとする。 X1 「-1 1 P 6 11 1-2 0|1|4 12 思考プロセス 母平均 m 母集団 母標準偏差 無作為 抽出 標本 個 公式の利用 E(X) =m 「標本平均の平均E(X) 【標本平均の標準偏差。(X) → 標本平均 X= = X1+X2+…+Xn n Action» 標本平均の平均は、母平均と同じであることを用いよ 解 (1) 母平均m=62,母標準偏差 o = 9, 標本の大きさ n = 100 より E(X)=m=62, o(X) 0 = n 9 9 o(X) = == 100 10 標本の大きさ, 母標準 偏差 6 のとき,標本平均 (2)母平均m, 母標準偏差 o は m=E(x)=(-1)/1/3 +0. +1. +2・ E(X₁²) = (−1)² . 1/3 +02. 6 14 4 1 2 12 1 +22. 1 12 1|2 a = o(X)= √E(X^*)-{E(X,)}=1-(1/2)=1/2 よって E(X)= =m= 2 (X)--- = 3 X の標準偏差は o(X) = - √n 標本の変量を X1,X2,..., Xn とすると =... =E(Xn)=m E(Xi) = E(X2) = 0(X1) = 0(X2) = == =o(Xn) = 0 V (X) = E(X2)-{E(X)} 3 2 3 2 標本の大きさ n=3

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英語 高校生

高校受験を控える弟の英語のテストなのですが、回答がなくて、どなたか回答案をくださりませんか?

7 次の(1),(2)の英文を読んで、それぞれの問いに答えなさい。 (1) ユタカ (Yutaka) とジョージ (George)は, 2人の住むみつば市 (Mitsuba City) について調査し,英語でプレ ゼンテーション(presentation)を行いました。 ユタカがスライド(slide)を使って発表をしています。 Hello, I'm Yutaka. I live in Mitsuba City and have lived there since I was born. There are some big parks in the city, and I often played in them with my friends when I was a child. I like my city very much. people than before. Look at Slide 1. Last month, I saw news about Mitsuba City on TV. It said that our city had fewer This shows the number of people in Mitsuba City. There were more than 300,000 people in 2000. The number became larger until 2010, but after that, it started to decrease. In 2020, about 280,000 people lived there. Why did the number of people become small? To find out the reasons, I read some books and checked some websites on the Internet. I got some ideas. Look at Slide 2. This shows the number of people in Wakaba City and Aoba City. These cities are next to Mitsuba City. You can see that these two cities had more people in 2020 than in 2000. In fact, Wakaba City started some plans to help parents in 2014. For example, parents don't have to pay money when they take their sick children to the hospital. This means parents can take care of their sick children ( A ) worrying about money. In Aoba City, a new train station was built in 2008. Since then, the city has more convenience stores, clothes shops, and restaurants. Living in Aoba City became more convenient, so more people started to live there. Look at Slide 3. You can see the number of each type of shop was larger in 2020 than in 2000. Now, Aoba City has become one of the most popular cities among people. Mitsuba City is a good city, but I don't think it has many attractive points. Parents still have to pay a lot of money to take care of their sick children. Also, there are not many shops and restaurants in the city. I think Mitsuba City should have more attractive points like Wakaba City and Aoba City. I want more people to live in Mitsuba City in the future. Slide 2 Slide 3 (people) 180,000 Covenience Stores 170,000 160,000 Clothes Shops 150,000 Restaurants 140,000 2000 2005 Wakaba 2010 2015 2020 --- Aoba (year) 0 10 20 30 40 50 (number) ■ 2000 m 2020 (注) be born 生まれる play 遊ぶ decrease 減少する in fact 実際は attractive 魅力的な find out take care of ~ news ニュース ~を探り出す ~ 〜の世話をする fewer より少ない website ウェブサイト convenient 便利な point -5-

未解決 回答数: 1