Statistics - Binomial Probability question

[theIBnerd]

Hi. i keep finding a different answer than what textbook offers. is my answer correct?

question: the quality control department of a company making computer chips knows that 2% of the chips arw defective. use the nurmal approximation to the binomial probability distribution, with a continuity correction, to find the probability that, in a batch containing 1000 chips, between 20 and 30 chips (inclusive) are defective.

my answer: probability=0.02
using TI 84+
binomcdf(1000,0.02,30)-binomcdf(1000,0.02,19)=0.5179 (its my answer)
but the textbook says the answer is: 0.5349

is there anything wrong with my solution? what do you think is the real answer?

thank you

 

[statdad]

You aren't using the continuity correction - you aren't even using the normal approximation.

 

[theIBnerd]

You aren't using the continuity correction - you aren't even using the normal approximation.

oh. i will work on that.

turns out my teacher has not said a single word on continuity correction and normal approximation. so i just assumed i could solve it using commulative thing.