Question 9.1: For the data in Table 9.1, find I, J1, ... , JI, N, X23, X3....

For the data in Table 9.1, find I, J_1, … , J_I, N, X_{23}, \bar{X}_3., \bar{X} .. ·

 TABLE 9.1 Brine II hardness of welds using four different fluxes
Flux Sample Values Sample Mean Sample Standard
 Deviation
A 250 264 256 260 239 253.8 9.7570
B 263 254 267 265 267 263.2 5.4037
C 257 279 269 273 277 271.0 8.7178
D 253 258 262 264 273 262.0 7.4498
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There are four samples, so I = 4. Each sample contains five observations, so J_1 = J_2 = J_3 = J_4 = 5. The total number of observations is N = 20. The quantity X_{23} is the third observation in the second sample, which is 267. The quantity \bar{X}_3. is the sample mean of the third sample. This value is \bar{X}_3 = 271.0. Finally, we use Equation (9.3) to compute the sample grand mean \bar{X}_{..}.

\bar{X}_{.,}=\frac{\sum_{i=1}^l J_i \bar{X}_i}{N}          (9.3)

\begin{aligned}\bar{X}_{. .}&=\frac{(5)(253.8)+(5)(263.2)+(5)(271.0)+(5)(262.0)}{20}\\&=262.5\end{aligned}

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