Restriction of Expected Cell Frequency to not less than

As mentioned at the beginning of this discussion of x h is not safe to use the test where any expected class frequency is less than 5. Sometimes this means that the test cannot be applied. On other occasions the difficulty can be evaded. 

It represents the data from which Table 5 in section (f) was built up. The expectations for cells LiB, and NaB are both less than 5. As the table stands, therefore, the x test cannot be applied. However, if we pool the data in columns Li and L, and in columns Nj and Nj, we get the 2x3 table quoted in section (f), Table 5,2, which is perfectly satisfactory. 

Consider a manufacturing process in which an operation is being repeated a great many times each day, and occasionally an inflammation occurs. If we set out in time sequence the daily number of inflammations we may get such a set of figures as 

Some days will be without any, others will have a relatively large number. The question we will discuss is whether the probability of obtaining an inflammation is cons)tant throughout. Prime facie we might consider that the days wit h 0 or 1 

---