Distinguishing between statistical and practical significance for a gender selection study

Intro

Howdy!  I'm Professor Curtis of Aspire Mountain Academy here with more statistics homework help.  Today we're going to learn how to distinguish between statistical and practical significance for a gender selection study.  Here's our problem statement: Determine whether the results appear to have statistical significance and also determine whether the results appear to have practical significance. I n a study of a gender selection method used to increase the likelihood of a baby being born a girl, 1,918 users of the method gave birth to 940 boys and 978 girls.  There is about a 20% chance of getting that many girls if the method had no effect.

Solution

OK, so what we need to do here is fill in the right selections for each of the different blanks in this statement that's been written for us.  And the first thing we're going to do to evaluate what's going on is calculate what do we actually have in our samples?  So the proportion of girls in the sample is going to be the number of girls divided by the total number of births.  So here I'm getting almost 51%.  So there's a 20% chance that this extra 1% bump I'm getting is completely by chance, which for statistical significance is not a whole lot going on there.  So we'd say that this does not have much statistical significance because the 20% chance of getting that randomly is actually fairly low.  If this number were greater than 50%, then we would probably say that it does have statistical significance, but here 20% is  relatively low. So we're going to say it doesn't have statistical significance.

And for an extra 1% bump, you're employing this method?  You know, I would say that not many people would be using this procedure because it doesn't really give you that much of a bump over the 50%.  I mean, we're asked to round to the nearest integer, so that would give us 51%.  And so we would say that this method doesn't have very much practical significance because you're only getting an extra 1% bump from using the methodology.  I mean, that's not a whole lot more guarantee of success for the outcome that you're looking for.  Nice work!

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