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Archive for the ‘Research’ Category

Systematic Review

For today’s post, you might want to open a second window at the Cochrane Collaboration Website so you can scroll through what is available while we talk. One thing I have been trying to communicate (over and over and over) is that each study is only one small piece of the puzzle researchers use to [...]

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Time to Event Techniques

Sometimes you want to understand the odds of an event that everyone in the group will not experience.  The best example in pregnancy and birth is the length of labor.  When you try to get an average length of labor you need to decide how to handle the labors that end in a cesarean birth. [...]

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Assessing Study Quality

We are nearly done with our discussion of statistics, so I wanted to take a day to discuss study quality. When researchers talk about the quality of a study they are considering the quality of the total package, not only the statistical significance of the findings. In fact, the quality of the study will affect [...]

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Statistics and Causation

One of the main reasons we invest our time into research (whether performing the science or reading the reports) is to understand how to avoid problems. We want to know what we can do to improve chances of a good outcome and have the best health.  We want to know what treatments are the most [...]

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Randomized Controlled Trial

We talked about a random sample last week.  Today we are going to talk about randomized controlled trials. The use of the term randomized in this context does not refer to the sampling method.  Randomized controlled trials use convenience sampling, meaning they recruit whoever is available and meets the enrollment criteria.  Because of this, randomized [...]

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Sampling Methods

On Wednesday we talked about why sample size matters.  Today I want to focus on how the sampling method affects the data. Basically, there are two ways to obtain a sample.  One way is to randomly select members of the population, and the other is to use whomever is available. To understand the difference, I [...]

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Why Sample Size Matters

On Monday we talked about regression techniques and I explained that finding a statistically significant result would be difficult because of our sample size.  Today we’ll explore how sample size affects the results you will get. To understand the importance of a sample size, you need to think back to our discussion about p-values and [...]

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Regression Techniques

Like the other statistical techniques we’ve talked about, regression techniques allow us to examine the relationship between two variables. But the regression techniques go a step beyond the Chi-Square and T-Test because they allow us to examine the relationship of multiple variables.  Unlike the previous tests, regression allows you to find the correlation of multiple [...]

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The T-Test

On Wednesday we used a T-Test to see if there was a difference in mean labor time between women who worked as a doula for income and those that worked as a doula for hobby. The next obvious question is, what is a T-Test and why did we choose to use it? Remember back to [...]

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What is a Confidence Interval?

On Monday we talked about how p-values tell us the probability of obtaining the result if the null hypothesis (the status quo) is true.  Today we turn our attention to the confidence interval and the additional information using a confidence interval provides. There are two things you need to remember to make sense of a [...]

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