4. Given the reliability for a measure, it is possible to estimate what the reliability of an alternative measure with a different number of items would be (assuming that the items are, on average, of equal quality) using the following formula, referred to as the Spearman-Brown Prophecy formula n*rtt Predicted reliablity = r'tt = 7+ (n-1) * r Where: r'tt = estimated reliability (new measure) Itt = calculated reliability (original measure) n=ratio of number of items on new measure to number on original measure a. If you currently have a 4 item measure with a reliability of 0.539, how many items would you need to obtain an estimated reliability of 0.7