SCENARIO 11-13
an Important Factor in Selecting Database Software Is

SCENARIO 11-13
An important factor in selecting database software is the time required for a user to learn how to use
the system. To evaluate three potential brands (A, B and C) of database software, a company
designed a test involving five different employees. To reduce variability due to differences among
employees, each of the five employees is trained on each of the three different brands. The amount of
time (in hours) needed to learn each of the three different brands is given below: $\begin{array}{ | r | r | r | r | } \hline & & \text { Software } & \\\hline \text { Operator } & \text { A } & \text { B } & \text { C } \\\hline 1 & 17 & 17 & 23 \\\hline 2 & 18 & 17 & 23 \\\hline 3 & 14 & 13 & 19 \\\hline 4 & 12 & 11 & 18 \\\hline 5 & 19 & 17 & 22 \\\hline \text { Mean } & 16 & 15 & 21 \\\hline\end{array}$

$\text { Below is the Excel output for the randomized block design: }$
$\begin{array}{lrrrrrr}\hline \text { Source of Variation } & S S & d f & \text { MS } & {\text { F }} & \text { P-value } & \text { Fcrit } \\\hline \text { Rows } & 84.66667 & 4 & 21.16667 & 50.8 & 9.98 \mathrm{E}-06 & 3.837853 \\\text { Columns } & 103.3333 & 2 & 51.66667 & 124 & 9.54 \mathrm{E}-07 & 4.45897 \\\text { Error } & 3.333333 & 8 & 0.416667 & & & \\\text { Total } & 191.3333 & 14 & & & & \\\hline\end{array}$
-Referring to Scenario 11-13, the randomized block F test is valid only if the
population of the amount of time needed has the same variance for the 3 brands.