Consider the following sample of observations on coating thickness for low-viscosity paint. 0.83 1.42 0.88 0.88 1.04 1.09 1.17 1.29 1.31 1.49 1.59 1.62 1.65 1.71 1.76 1.83
(a)
Calculated point estimate of the mean value of coating thickness is : . (Rounded of my answer to four decimal places.)
1.3475
(b)
The point estimate of the population median can be obtained from the sample median. In this case, since there are 16 data values, the sample median will be the average of the 8th and 9th data values in the ordered data set. The 8th value is 1.31 and the 9th value is 1.42, so the median will be calculated as follows:
Median = (1.31 + 1.42) / 2 = 1.365
Therefore, the point estimate of the population median is 1.365.
(c)
First we need to find the standard deviation of the data. Following table shows the calculations:
X | (X-mean)^2 | |
0.83 | 0.267 | |
0.88 | 0.2185 | |
0.88 | 0.2185 | |
1.04 | 0.0945 | |
1.09 | 0.0663 | |
1.17 | 0.0315 | |
1.29 | 0.0030 | |
1.31 | 0.0014 | |
1.42 | 0.0052 | |
1.49 | 0.0203 | |
1.59 | 0.05880 | |
1.62 | 0.07425 | |
1.65 | 0.09150 | |
1.71 | 0.1314 | |
1.76 | 0.1701 | |
1.83 | 0.2328 | |
Total | 21.56 | 1.7555 |
Now we need z-score that has 0.10 area to its left. The z-score -1.28 has 0.10 area to its left. Since data is distributed normally so the required value is
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