Statistics question please help!

5.3, 7.2, 5.5, 6.5, 5.7, 4.7, 7.5, 7.5, 7.1, 5.4, 5.4, 4.4, 5.7, 6.3, 4.2, 7.1
the above is the data of an experiment that was done 16 times (16 numbers).

the first question was What percentage of outcomes are less than or equal to 5.0 seconds? i calculated 18.75%
the next question is
What percentage of outcomes are within one standard deviation of the mean?
i cant figure out how to solve this , im really stuck !! please help! if you can show me how to do this one i can perhaps figure out the next one which is what percentage of outcomes are within 2 standard deviation of the mean..... I know that the rule is 68% in one and 95 in 2 (if its a normal distribution, but i dont know how to tell if it is!! )

Thanks so much !!

What percentage of outcomes are less than or equal to 5.0 seconds?

3/16 = 0.1875*100 = 18.75%, right!

Mean = 5.96875

SD = 1.0897821

5.96875 - 1.0897821 = 4.88

5.96875 + 1.0897821 = 7.06

P(4.88 ≤ X ≤ 7.06) = 8/16 = 0.5*100 = 50%

Calculate the mean and the standard deviation(sd) of the data set.

Count the number of data points between mean + sd and mean - sd.