A missing value in a 2⁴ factorial. It is not unusual to find that one of the observations in a 2^k design is missing due to faulty measuring equipment, a spoiled test, or some other reason. If the design is replicated n times (n > 1) some of the techniques discussed in Chapter 5 can be employed. However, for an unreplicated factorial (n = 1) some other method must be used. One logical approach is to estimate the missing value with a number that makes the highest-order interaction contrast zero. Apply this technique to the experiment in Example 6-2 assuming that run ab is missing. Compare the results with the results of Example 6-2.