A student is trying to decide if it is cheaper to order blank CDs over the Internet or to buy them at local electronics stores.Listed below are the prices (in dollars)quoted for boxes of 200 blank CDs from various manufacturers. $$\begin{array} { c c }
\ \text { Internet } & \text { Local Electronics Stores } \
26.00& 33.98 \
27.99& 37.75 \
31.50 & 38.99 \
32.75 & 35.79 \
27.00 & 33.99 \
27.98 & 34.79 \
24.75 & 29.98 \
28.15& 33.00 \
29.99 & 32.00\
29.99
\end{array}$$
On the average,can we conclude that Internet purchases are significantly less than electronics store purchases? Test at ? = .05
A)Reject the null hypothesis;Internet purchases are less than local stores.
B)Do not reject the null hypothesis;there is not enough evidence to show that Internet purchases are less than local stores.
$$\begin{array} { l c }
\text { }&\text { Internet } & \text { Local Electronics Stores } \
\text { }& 2 & 14 \
\text { }&5 & 18 \
\text { }&10 & 19 \
\text { }&12 & 17 \
\text { }&3 & 15 \
\text { }&4 & 16 \
\text { }&1 & 7 \
\text { }&6 & 13 \
\text { }&8.5 & 11 \
\text { }&8.5 & \
\text { TOTAL }&60 & 130
\end{array}$$

Question

A student is trying to decide if it is cheaper to order blank CDs over the Internet or to buy them at local electronics stores.Listed below are the prices (in dollars)quoted for boxes of 200 blank CDs from various manufacturers. $$\begin{array} { c c } 
\ \text { Internet }  & \text { Local Electronics Stores } \
26.00& 33.98 \
27.99& 37.75 \
31.50 & 38.99 \
32.75 & 35.79 \
27.00 & 33.99 \
27.98 & 34.79 \
24.75 & 29.98 \
28.15& 33.00 \
29.99 & 32.00\
29.99
\end{array}$$
On the average,can we conclude that Internet purchases are significantly less than electronics store purchases? Test at ? = .05
A)Reject the null hypothesis;Internet purchases are less than local stores.
B)Do not reject the null hypothesis;there is not enough evidence to show that Internet purchases are less than local stores.
$$\begin{array} { l c } 
 \text {  }&\text { Internet } & \text { Local Electronics Stores } \
 \text {  }& 2 & 14 \
 \text {  }&5 & 18 \
 \text {  }&10 & 19 \
 \text {  }&12 & 17 \
 \text {  }&3 & 15 \
 \text {  }&4 & 16 \
 \text {  }&1 & 7 \
 \text {  }&6 & 13 \
 \text {  }&8.5 & 11 \
 \text {  }&8.5 & \
 \text { TOTAL }&60 & 130
\end{array}$$

Quizplus · Accepted Answer

We can use a two-sample t-test to compare the means of the Internet and local electronics store prices. Using a calculator or software, we find that the sample mean for Internet prices is 28.31 and the sample mean for local electronics store prices is 34.58. The pooled standard deviation is 4.23. The t-test statistic is calculated as (28.31 - 34.58) / (4.23 / sqrt(90)) = -5.41. This has a p-value much less than 0.05, indicating strong evidence against the null hypothesis that there is no difference in means. Therefore, we reject the null hypothesis and choose answer A: Reject the null hypothesis; Internet purchases are less than local stores.

A Student Is Trying to Decide If It Is Cheaper