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Suggested answer to exercise: Locomotor milestones and babywalkers, 2

Question 2: In the table, the difference in mean time to stand alone was 3.32 weeks,
(95% confidence interval 4.87 to 1.77).
What does this statement mean and what can we conclude?

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Suggested answer

We calculate a 95% confidence interval when we want a sample to tell us something
about the larger population from which is drawn.
We estimate that the difference for the whole population is within the interval.
The interval is chosen so that 95% of intervals will contain their population value.

We estimate here that the average time at which all babies using baby walkers
first stand alone is between 1.77 and 4.87 weeks
later than the average time at which all babies who do not use baby walkers first stand alone,
in this population.

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Last updated: 23 October, 2006.

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