The 68-95-99.7 rule states that in a normal distribution: a. The probability of a random value to be within 2 standard deviations above the mean is 95%. b. 95% of all values are within 2 standard deviations from the mean c. The probability of a random value to be 2 standard deviations above the mean of 2 standard deviations below the mean is 95% d. The probability of a random value to be between 1 and 2 standard deviations above the mean is 95%