91影视

Mean $渭=26.8$

Standard deviation, $蟽=7.4$

BMI$x=18.5$

Calculate the z - score,

$z=\frac{x-渭}{蟽}=\frac{18.5-26.8}{7.4}鈮�-1.12$

To find the corresponding probability, use the normal probability table in the appendix.

See the row that starts with $-1.1$and the column that starts with $.02$of the standard normal probability table for $P(z<-1.12)$

$P(x<18.5)=P(z<-1.12)=0.1314$

$A:$A young woman from the United States is underweight.

$B:$At least one of the two women from the United States is underweight.

$A^c:$One American young woman is not underweight.

$B^c:$Neither of the two American young women is underweight.

One American young woman is now at risk of being underweight.

$P(\mathrm{A})=0.1314$

Apply the complement rule to determine whether or not one American is underweight:

$P\left({\mathrm{A}}^{\mathrm{c}}\right)=1-P(\mathrm{A})=1-0.1314=0.8686$

Because the young women from the United States were chosen at random, it would be more convenient to assume that they are all independent of one another.

Therefore,

Apply the complement rule:

$P(\mathrm{B})=P\left({\left({\mathrm{B}}^{\mathrm{c}}\right)}^{\mathrm{c}}\right)=1-P\left({\mathrm{B}}^{\mathrm{c}}\right)=1-0.7545=0.2455$

Therefore,

Mean, $渭=26.8$

Standard deviation,$蟽=7.4$

Calculate the z-score,

$z=\frac{x-渭}{蟽}=\frac{18.5-26.8}{7.4}鈮�-1.12$

To find the corresponding probability, use the normal probability table in the appendix

See the row that starts with $-1.1$and the column that starts with $.02$of the standard normal probability table for $P(z<-1.12)$

$$\begin{gathered} P(x<18.5)=P(z<-1.12) \\ =0.1314 \\ =13.14\% \end{gathered}$$

Therefore, Around $13.14\%$of young women have a BMI (Body Mass Index) of less than $18.5$and are underweight.