Final answer:
Using the range rule of thumb and a mean of 1188.5 cm3 with a standard deviation of 129.8 cm3, values below 928.9 cm3 or above 1448.1 cm3 are significantly low or high. A brain volume of 1478.1 cm3 is significantly high as it exceeds the upper limit.
Step-by-step explanation:
To identify the limits separating values that are significantly low or significantly high using the range rule of thumb, we can calculate these limits by adding and subtracting multiples of the standard deviation from the mean. Since the mean brain volume is 1188.5 cm3 and the standard deviation is 129.8 cm3, let's apply the rule of thumb.
Typically, values more than two standard deviations from the mean are considered significant. Therefore, the lower limit is given by 1188.5 - (2 × 129.8) = 928.9 cm3 and the upper limit is 1188.5 + (2 × 129.8) = 1448.1 cm3. Thus, any brain volume less than 928.9 cm3 or more than 1448.1 cm3 is considered significantly low or high, respectively.
A brain volume of 1478.1 cm3 would be considered significantly high because it exceeds the upper limit of 1448.1 cm3.