a set of data has a normal distribution with a mean of 120 and a standard deviation of 10. Find the interval about the mean within 90% of the data lie

Question

amistre64 · Answer

since the mean is 50% of the data, and 90/2 = 45

you want z values that correspond to 50-45  and 50+45

amistre64 · Answer

i take it that made perfect sense :)

amistre64 · Answer

z1 = -1.645

z2 =  1.645

$$z_n=\frac{x-mean}{sd}$$
$$z_n(sd)+mean=x$$
$$\pm1.645(10+120)=x_1,x_2$$

amistre64 · Answer

latex fail :)

$$\pm1.645(10)+120=x_1,x_2$$

anonymous · Answer

so the choices are:
 94.2-145.8
103.5-136.5
113.68-126.32
100.4-139.6

amistre64 · Answer

so about, 120 - 16 and 120 + 16

anonymous · Answer

ohh thanks!