Stereograms appear to be composed entirely of random dots. However, they containseparate images that a viewer can "fuse" into a threedimensional (3D) image by staring at the dots while defocusing the eyes. An experiment was performed to determine whether knowledge of the form of the embedded image affected the time required for subjects to fuse the images. One group of subjects (group NV) received no information or just verbalinformation about the shape of the embedded object. A second group (group W) received both verbal information and visual information (specifically, a drawing of the object). The experimenters measured how many seconds it took for the subject to report that he or she saw the 3D image. 2-Sample t-interval for 1 - 2 df = 70 Conf level = 90% (NV) - (W) interval: (0.55, 5.47).

c) What's the margin of error for this interval?

d) What does the 90% confidence level mean.

e) Would you expect a 99% confidence level to bewider or narrower? Why?

f) Might that change your conclusion in part b? How?