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Maternity Experiences Survey, 2006 – User Guide
CI xˆ = {0.707 – 0.057, 0.707 + 0.057}
CI xˆ = {0.650, 0.764}
With 95% confidence it can be said that between 65.0% and 76.4% of women whose
primary caregiver at birth was a midwife rated their labour and birth experiences as “very
positive”.
10.3 How to Use the Coefficient of Variation Tables to Do a
T-test
Standard errors may also be used to perform hypothesis testing, a procedure for distinguishing
between population parameters using sample estimates. The sample estimates can be numbers,
averages, percentages, ratios, etc. Tests may be performed at various levels of significance,
where a level of significance is the probability of concluding that the characteristics are different
when, in fact, they are identical.
Let X̂ 1 and X̂ 2 be sample estimates for two characteristics of interest. Let the standard error on
the difference Xˆ 1 − Xˆ 2 be
If t =
Xˆ 1 − Xˆ 2
σ dˆ
σ d̂ .
is between -2 and 2, then no conclusion about the difference between the
characteristics is justified at the 5% level of significance. If however, this ratio is smaller than -2
or larger than +2, the observed difference is significant at the 0.05 level. That is to say that the
difference between the estimates is significant.
10.3.1
Example of Using the Coefficient of Variation
Tables to Do a T-test.
Let us suppose that the user wishes to test, at 5% level of significance, the hypothesis
that there is no difference between the proportion of women whose primary caregiver at
birth was a midwife and the proportion of women whose primary caregiver at birth was an
obstetrician, gynaecologist, family doctor or nurse or nurse practitioner, and who rated
their labour and birth experiences as “very positive”. From Example 3, Section 10.1.1, the
standard error of the difference between these two estimates was found to be 0.02937.
Hence,
t=
Xˆ 1 − Xˆ 2
σ dˆ
=
0.707 − 0.529
0.178
=
= 6.06
0.02937
0.02937
Since t = 6.06 is greater than 2, it must be concluded that there is a significant difference
between the two estimates at the 0.05 level of significance.
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Special Surveys Division