Contents

CHAPTER 11: Data Analysis and Interpretation: Part I. Describing Data, Confidence Intervals, Correlation 367FIGURE 11.2Infants’ understanding of the nature of pictures was examined by observing how they investigateand point to pictured objects. (Research conducted by Dr. Alma Gottlieb among Beng infants inIvory Coast from DeLoache, et al., 1998)Coast)” manually explored and grasped at the pictures (including picturesof objects common in the Beng community) in the same way as Americaninfants (Study 3). (See Figure 11.2.)The purpose of the fourth study was to determine how children’s behavior towardpictures changes with age.Three age groups were tested: 9-month-olds, 15-month-olds, and 19-montholds.Each group had 16 children, 8 girls and 8 boys. In addition to observingchildren’s behaviors of investigating the pictures with their hands (graspingand other investigative behaviors), the researchers coded instances of pointingat pictured objects. Their results for infants’ investigative behaviors are shownin Figure 11.3.The independent variable, age of the children, is a natural groups designwith three levels: 9 months, 15 months, and 19 months. This variable appearson the horizontal axis (x-axis). The dependent variable was number of investigativebehaviors, and the mean number of these behaviors appears onthe vertical axis (y-axis). As you can see in Figure 11.3, the mean numberof investigative behaviors is highest for 9-month-olds, and much lower for15-month-olds and 19-month-olds. The other important piece of informationin the figure is the “bars” that surround each mean. We can use these bars tomake decisions about whether there was an effect of the independent variable,age.The bars around each mean in Figure 11.3 represent confidence intervals. Asyou have learned, confidence intervals tell us about the range of values we canexpect for a population value. We cannot estimate the population value preciselybecause of sampling error, but we can estimate a range of probable values. Thesmaller the range of values expressed in our confidence interval, the better is our