Step 1 :The z-score is a measure of how many standard deviations an element is from the mean. To find the z-score of a value, we subtract the mean from the value and then divide by the standard deviation. In this case, the mean is 1529 and the standard deviation is 311. We can calculate the z-scores for each of the four students' test scores using this formula.
Step 2 :A z-score of less than -2 or greater than 2 is generally considered unusual. After calculating the z-scores, we can check if any of them fall outside this range.
Step 3 :Calculate the z-scores for the test scores 1960, 1260, 2220, and 1430. The z-scores are approximately 1.39, -0.86, 2.22, and -0.32 respectively.
Step 4 :Check if any of the z-scores fall outside the range of -2 to 2. The test score 2220 is considered unusual as its z-score is greater than 2.
Step 5 :\(\boxed{2220}\) is the unusual value.