Distribuições, transformações e dispersão
SAT Tópico 14 3:36 Narração em inglês · Legendas em inglês + 中文 gravadas
Capítulos
Transcrição
A frequency counts repeated observations.
频率表示重复观测的次数。
Values one, three, seven with frequencies two, one, one represent four observations: one, one, three, seven.
数值1、3、7对应的频数分别为2、1、1，代表四次观测：1、1、3、7。
X bar equals sum of f times x divided by sum of f, which is two times one plus one times three plus one times seven, all over four, equals three.
x平均等于f乘x的总和除以f的总和，即2乘1加1乘3加1乘7，整体除以4，结果为3。
The median is one plus three, all over two, equals two.
中位数为1加3除以2，等于2。
It need not equal the mean.
它不一定等于均值。
Each task gives its own data.
每个任务都有各自的数据。
Do not copy the worked example’s numbers.
请勿照搬示例中的数值。
Pause here and attempt the task before revealing the reasoning.
请先暂停，完成这道练习再继续。
Use the full context on the preceding pages.
请结合前几页的完整背景信息作答。
The data are 2, 2, 2, 5, 5, 8.
数据是二、二、二、五、五、八。
The mean is 3 times 2, plus 2 times 5, plus 8, all over 6, which is 4.
平均数等于三乘二加二乘五加八，再除以六，等于四。
The median is the average of the third and fourth values, 2 plus 5 over 2, which is 3.5.
中位数是第三和第四个数的平均，即二加五除以二，等于三点五。
The range is 8 minus 2, which is 6.
极差是八减二，等于六。
Pause here and attempt the task before revealing the reasoning.
请先暂停，完成这道原创练习再继续。
Use the full context on the preceding pages.
请利用前几页的完整背景信息。
The new mean is 3 times the old mean, minus 4, which is 3 times 4 minus 4, or 8.
新的平均数等于三倍原平均数减四，即三乘四减四，等于八。
The median is 3 times 3.5 minus 4, which is 6.5.
中位数是三乘三点五减四，等于六点五。
The range is 3 times 6, which is 18.
极差是三乘六，等于十八。
The standard deviation triples; subtracting 4 changes no distance from the mean.
标准差变为原来的三倍；减四不会改变任何数据到平均数的距离。
Pause here and attempt the task before revealing the reasoning.
请先暂停，完成这道原创练习再继续。
Use the full context on the preceding pages.
请利用前几页的完整背景信息。
Both means are 5.
两组的平均数都是五。
Every A observation is 5 from its mean; B distances are 5,0,0,5.
A 的每个观测值离平均数都是五；B 的距离分别是五、零、零、五。
B therefore has smaller mean squared deviation and smaller standard deviation.
所以 B 的平均平方离差更小，标准差也更小。
Equal range alone is insufficient.
只看极差相等是不够的。
Return to the task and explain why the method fits.
回到该任务，并解释为何此方法适用。
Original practice does not predict an official score.
原始练习无法预测正式成绩。
Complete required live or recorded evidence separately.
请单独完成所需的现场或录制证据。
Pause and test yourself. Cover the worked answer, rebuild the answer to the last example in your own words, and name one condition that would change it before you check.
暂停一下，自我检测：遮住示范答案，用自己的话重做最后一个例子的答案，并在核对之前说出一个会改变结论的条件。