1. Develop 90% confidence interval for Biparietal distance for neonatal infants based on the data available in the case for babies who are 1-2kg, 2-3kg and 3-4kg in weight. [HINT: One interval for each group; therefore, three total intervals.]
2. How would you interpret these three intervals? Be specific and interpret the result for each group.
3. For each weight group, compare the confidence interval width (i.e., the entire width from the lower limit to the upper limit) to the mean as a percent. What conclusions can you draw about this percent? [HINT: How does the percentage vary by weight group?]
4. Suppose you wanted to predict the baby's Biparietal distance with more precision. The design team claims that it must have more precise and accurate estimates of this measure to ensure that the device fits properly for each baby. In fact they would like to have the half-interval, h, be less than 3 % of the mean value. How many babies would you need to sample in each group to have this be the case? Maintain 90 % confidence.