A candy company wants to identify whether or not the size of its?
candy bars are the same length from one day to another. On day 1 they
sample 52 candy bars with an average mean of 5.4 inches and on day 2
they sample 52 bars again with and average mean of 5.6 inches. Both
days have sample standard deviations of 3.4. Is the average mean of
size different from day 1 to day 2?

A simple way to solve this would be using the student t-test Xavg±
2.776 /N^(1/2) for a 95% confidence interval.  This implies that 95%
of your data will lie within the limits from the equation above.

So since you have same standard deviation and sample size but
different means => the two means are different. the length of the
candy bar was statistically different on both days.