The birth weights for two groups of babies were compared in a study. In one group the mothers took a zinc supplement during pregnancy. In another group, the mothers took a placebo. A sample of 165 babies in the zinc group had a mean birth weight of 3402 grams. A sample of 127 babies in the placebo group had a mean birth weight of 3027 grams. Assume the standard deviation is known to be 723 grams for the population of babies whose mothers took a zinc supplement during pregnancy and 791 grams for babies whose mothers did not. Determine the 98 % confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies. Step 1 of 2: Find the critical value that should be used in constructing the confidence interval.
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
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