21 Lab 6: The Normal Distribution

21.0.1 Our data

The dataset we’ll be working with in this lab comes from the Stat Labs data repository at the University of California, Berkeley. We will be using the “Birth weight I” dataset. Below is a description of its contents from the Stat Labs book.

The data available for this lab are a subset of a much larger study — the Child Health and Development Studies (Yerushalmy [Yer64]). The entire CHDS database includes all pregnancies that occurred between 1960 and 1967 among women in the Kaiser Foundation Health Plan in Oakland, California. The Kaiser Health Plan is a prepaid medical care program. The women in the study were all those enrolled in the Kaiser Plan who had obtained prenatal care in the San Francisco–East Bay area and who delivered at any of the Kaiser hospitals in Northern California.

[…]

At birth, measurements on the baby were recorded. They included the baby’s length, weight, and head circumference. Provided here is a subset of this information collected for 1236 babies — those baby boys born during one year of the study who lived at least 28 days and who were single births (i.e., not one of a twin or triplet). The information available for each baby is birth weight and whether or not the mother smoked during her pregnancy.

The birth weight of each baby was recorded in ounces.

1. Download and clean the “Birth weight I” data from the link below.

https://www.stat.berkeley.edu/users/statlabs/labs.html

When your cleaning process is finished, the first six rows of your data should look like the printout below.

``````##   bwt smoke
## 1 120    No
## 2 113    No
## 3 128   Yes
## 4 123    No
## 5 108   Yes
## 6 136    No``````
1. Using the definition of “low birth weight” from the tutorial, what is the proportion of babies in this sample that can be classified as low birth weight?

2. Using the same definition of “low birth weight”, what is the proportion of babies in this sample among mothers who were not smokers that can be classified as low birth weight?

3. Using the same definition of “low birth weight”, what is the proportionn of babies in this sample among mothers who were smokers that can be classified as low birth weight?

4. What is the smoker vs. non-smoker ratio of low weight births in this sample?

5. Reproduce the plot below. Explain what it tells us. Feel free to use information you used to answer previous questions in this lab to support your explanation.

Extra credit: What was your birth weight in ounces? Use this information to report your birth weight percentile.