Question

95% of a standard curve falls within how many SD's away from the mean?

(A) 1
(B) 2
(C) 3
(D) 4

Answer 1

In a standard curve, 95% of the data falls within two standard deviations from the mean, so the correct option is (B) 2.

Step-by-step explanation:

The student has asked how many standard deviations (SD's) away from the mean include 95% of the data in a standard curve. This is a question related to the Empirical Rule, which is a statistical rule stating that for a normal distribution:

• Approximately 68% of the data falls within one standard deviation of the mean.
• Approximately 95% of the data falls within two standard deviations of the mean.
• More than 99% of the data falls within three standard deviations of the mean.

Therefore, the correct option is (B) 2. This means that if we have a normal distribution (often referred to as a bell-shaped curve), 95% of the observations are expected to lie within two standard deviations (above or below) from the mean.