Question: In a study of intra-observer variability in the assessment of cervical smears, 3325 slides were screened for the presence or absence of abnormal squamous cells.

Each slide was screened by a particular observer and then re-screened six months later by the same observer. The slides were coded so the screener was “blind” to the fact that the same slides were submitted for review a second time.

The results of this study are abstracted in Table Question 1.

Intra-observer assessment in two readings of the same slides by the same reader with a time interval of 6 months.

a) In the study design employed, what kind of Chi Square test is appropriate to examine the question of intra-observer reliability? Note: we had two different applications of the Chi-Square to analyze data from independent and non-dependent designs.

b) Carry out the appropriate Chi-Square test to examine the question whether the data support the null hypothesis that there is no association (consistency) between the observers screening diagnosis results over the two time periods.

c) From the point of view of intra-observer reliability. If the data indicates that you accept the null hypothesis, is this a “good result” in terms of diagnostic outcome or not?