The cutoff score for intellectual disability is approximately two standard deviations below the mean.
if iq scores were normally distributed, this would mean that approximately percent of the population would fall below this cutoff.

2.5%

Explanation:

When considering a normal distribution as stated here, the Empirical rule is used for approximation. For two standard deviations, Empirical rule suggests that 95% of the data would fall within two standard deviations. This means that 5% of the data would be outside the two standard deviation mark. This means that 2.5% of the population would fall outside the two standard deviation mark 'below' the mean and 2.5% of the population would fall outside the two standard deviation mark 'above' the mean. Here, the percentage that is required is the one that falls below cutoff or two standard deviations below the mean which is 2.5%.

answer; (true);

answer; decreased;