Learn By Doing – Case C-C (Software)

Published: December 23rd, 2012

Category: Activity 1: Learn By Doing, Learning Statistical Software

Use the solutions provided and complete the questions for practice with Case C-C.

Optional: Create your own solutions using your software for extra practice.


In this activity, we will use the collected data to:

  • build a two-way table and compute conditional percentages.
  • interpret the data in terms of the relationship between a young child’s nighttime exposure to light and later nearsightedness.


Use the output to answer the questions that follow.

Background Information for Dataset

An Associated Press article captured the attention of readers with the headline “Night lights bad for kids?” The article was based on a 1999 study at the University of Pennsylvania and Children’s Hospital of Philadelphia, in which parents were surveyed about the lighting conditions under which their children slept between birth and age 2 (lamp, night-light, or no light) and whether or not their children developed nearsightedness (myopia). The purpose of the study was to explore the effect of a young child’s nighttime exposure to light on later nearsightedness.


nightlight.xls or nightlight.csv

Learn By Doing






(Optional) SPSS Steps:

  • Create Two-Way tables: ANALYZE > DESCRIPTIVE STATISTICS > CROSSTABS, complete the wizard (4 times) to obtain
    • Two-way table with the count (frequency) and percent (out of total)
    • Two-way table with the count (frequency) and row percents
    • Two-way table with the count (frequency) and column percents
    • Two-way table with the count (frequency), row and column percents

(Optional) SAS Steps:

  • Create Two-Way tables: Use PROC FREQ and the tables statement to create a two-way table with light and nearsightedness

This document is linked from Case C-C.