The percentage of young adults who send fewer than 218 text messages is 99.87%.
For a normally distributed set of data, given the mean and standard deviation, the probability can be determined by solving the z-score and using the z-table.
First, solve for the z-score using the formula below.
z-score = (x – μ) / σ
where x = individual data value = 218
μ = mean = 128
σ = standard deviation = 30
z-score = (218 - 128) / 30
z-score = 90 / 30
z-score = 3
Find the probability that corresponds to the z-score in the z-table. (see attached images)
z-score = 3
probability = 0.9987
To get the percentage, multiply the probability by 100.
percentage = probability x 100
percentage = 0.9987 x 100
percentage = 99.87%
Learn more about probability here: brainly.com/question/26822684
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