91Ó°ÊÓ

Number of newborns $=400,000$

Number of period$=6yearperiod$

Meanlocalid="1649405246193" $=3668grams$

Standard deviation$=511grams$

No. of babies weight less than localid="1649405770830" $2500grams=17babies$

Given:

$\begin{array}{r}\mathrm{μ}=3668\end{array}$

$\mathrm{σ}=511$

$x=2500$

The z-score is the value $x$decreased by the mean, divided by the standard deviation:

localid="1649917213420" $$\begin{gathered} z=\frac{x-\mathrm{μ}}{\mathrm{σ}} \\ =\frac{2500−3668}{511} \\ =-2.29 \end{gathered}$$

Using table A: Determine the corresponding probability

localid="1649917222116" $$\begin{gathered} P(x<2500)=P(z<-2.29) \\ =0.0110 \\ =1.10\% \end{gathered}$$

Number of newborns$=400,000$

Number of periodlocalid="1649405893329" $=6yearperiod$

Mean$=3668grams$

Standard deviation$=511grams$

No. of babies weight less than$2500grams=17babies$

Given:

$\mathrm{μ}=3668$

$\mathrm{σ}=511$

$x=2500$

The quartiles correspond with a probability of $0.25$and $0.75$in table A:

$z=Â\pm 0.67$

The corresponding values are then the mean multiplied by the standard deviation in addition to the z-score:

localid="1649917232279" $$\begin{gathered} x=\mathrm{μ}-z\mathrm{σ} \\ =3668-0.67\left(511\right) \\ =3325.63 \end{gathered}$$

localid="1649917237241" $$\begin{gathered} x=\mathrm{μ}+z\mathrm{σ} \\ =3668+0.67\left(511\right) \\ =4010.37 \end{gathered}$$