91影视

The number of checks issued by a suspect company is$n=784$.

The probability of a check having a lead digit of 鈥�1鈥檌s $p=0.301$.

a.

The expectednumber of checks among the 784 that should have a leading digit of 1 is computed as follows.

$$\begin{gathered} 渭=np \\ =784脳0.301 \\ =235.984 \\ 鈮�236.0 \end{gathered}$$

Therefore, theexpectednumber of checks among the 784 that should have a leading digit of 1 is236.0.

b.

The mean number of checks among the 784 that should have a leading digit of 1 is computed as follows.

$$\begin{gathered} 渭=np \\ =784脳0.301 \\ =235.984 \\ 鈮�236 \end{gathered}$$

Thus, the mean is 236 checks.

The standard deviation of thenumber of checks among the 784 that should have a leading digit of 1 is computed as follows.

$$\begin{gathered} 蟽=\sqrt{np\left(1-p\right)} \\ =\sqrt{784脳0.301脳\left(1-0.301\right)} \\ =12.84 \\ 鈮�12.8 \end{gathered}$$

.

Therefore, the standard deviation of the number of checks among the 784 that should have a leading digit of 1 is 12.8 checks.

c.

Using the range rule of thumb, we get that the significant low values are the values less than $渭-2蟽$.

The calculation is as follows.

$$\begin{gathered} 渭-2蟽=236.0-\left(2脳12.8\right) \\ =210.4 \end{gathered}$$

Therefore, the significant low values are the values that are less than 210.4 checks.

d.

It can be observed that 0 is less than or equal to 210.4.

Therefore, there isstrong evidence that the suspect checks are very different from the expected results.