7. Consider the following graph of the mean yield of barley in 1980, 1984, and 1988 along with a 95% confidence interval . 1988 1984 1 950 140 160 180 200 220 240 260 280 Yield (g/400m) Which of the following is INCORRECT? (a) Since the confidence intervals for 1984 and 1980 have considerable overlap, there is little evidence that the sample means differ. (b) Since the confidence intervals for 1988 and 1980 do not overlap, there is good evidence that their respective population means differ (c) The sample mean for 1984 is about 195 g/400m. (d) The sample mean for 1988 is less than the sample mean for 1984. (e) The estimate of the population mean in 1938 is more precise than that for 1980 since the confidence interval for 1983 is narrower than that for 1980