Now let’s take a look behind the scenes to explore how statistical theory is used to create what is called a sampling distribution of the sample mean. Statistically speaking, there is sufficient evidence to suggest that the levels of DDE contamination are too high among South African women. This probability is low enough that there is reason for concern. The probability of the DDE contamination in the women’s bodies exceeding 10 mg/kg (if there were no contamination) is approximately 0.02.
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In this study, there was a lot of evidence that the mean DDE contamination in the pregnant women was greater than 10 mg/kg.
ONLINE STATBOOK SAMPLING DISTRIBUTIONS APPLET FULL
But the good news is that statistical theory provides us with just the tools we need to be able to use our single sample in a meaningful way to make inference about the full population. Were it not for statistical theory, the results from our single sample would essentially be worthless. This is how research is often conducted…repeated samples are not typically drawn, so we do not get to know what might have happened had we gathered data from a different sample. The researchers do not get to see the contamination levels for any other women.
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If the researchers had selected a different random sample of pregnant women, the mean contamination of the women in the sample would undoubtedly be different. An important question to ask at this point is whether or not the results of this sample show evidence that the mean DDE contamination in the full population of South American women was greater than 10 mg/kg. They only had enough time, funding, and other resources to survey the 45 women in their sample. The researchers only obtained one sample mean, \(\bar x\). They found the mean observed contamination level was 24.75 mg/kg, and the highest level of contamination was 419.91 mg/kg! (Bornman, MS. The researchers computed the mean and standard deviation of the observed levels of exposure for the 45 women. These data will be used to assess the prevalence of DDT in drinking water.Īfter selecting specific women to be sampled, researchers measured the level of DDE contamination for each of these randomly selected women. Global Solutions Unlimited (GSU) will analyze the data from this study. When a pregnant woman has a contamination level as low as 10 mg/kg of DDE in her body, she is much more likely to give birth to an underweight baby or to deliver prematurely (Wells & Leonard, 2006).Ī study of 45 pregnant women who have been exposed to DDT / DDE was conducted using a convenience sample (Bornman, MS. Scientists have shown that DDT and its metabolites cause reproductive problems in humans and other animals. When DDT is broken down in humans, DDE is one of the metabolites that remains from the original DDT. A metabolite is the byproduct that occurs when our body breaks down a substance. Unfortunately, this pesticide does not break down quickly in nature and is very harmful to humans.Ī metabolite of DDT (called DDE) is also very dangerous. In an attempt to curb the spread of malaria and save lives, the pesticide DDT was used for many years to control the insect population, even indoors. Mosquitoes and other biting insects carry malaria.
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Case Study: DDT’s Negative Impact on Pregnant Women