The scores 3, 5, 6, 7, 8, 5, 3, 5 have a mean 5.26 and standard deviation 1.64. How many of these scores are more than 1 standard deviation from the mean?
lower limit 5.26 – 1.64 = 3.62
upper limit 5.26 + 1.64 = 6.9
so you just count the scores under 3.62 and more than: 6.9 3, 7, 8, 3
∴ 4 scores