The weights of 1000 children have an average of 45 kilograms and a standard deviation of 5 kilograms.

Question

Situation: You volunteered to be part of the medical mission in your barangay and in-charge to get weight of the children. The weights of 1000 children have an average of 45 kilograms and a standard deviation of 5 kilograms.

Estimate the range of the number of children weighing

1.below 55 kg (is 523 the correct answer?)

2.between 25 kg to 58kg (is 995 the correct answer?)

using z table

Answer 1

Hi Music S.,

Please get a standard distribution plot showing z-scores and cumulative probabilities. You will see that below 55 kg, which is two standard deviations above the average, there are 97.7% of the population. Does that look about the right size for 523/1000? If not, the calculation is right there waiting for you! Now look at that same distribution plot, and figure out where the 25 to 58 kg range will fall. I hope you calculate it as (25-45)/5 = -4 to (58.5-45)/5 = +2.5. So 995 looks about right, maybe 994. Who's counting, it's an estimate anyway.

-- Cheers, --Mr. d.