In: Math
A fish story: The mean length of one-year-old spotted flounder, in millimeters, is 133 with standard deviation of 20, and the mean length of two-year-old spotted flounder is 156 with a standard deviation of 24. The distribution of flounder lengths is approximately bell-shaped.
(a) Anna caught a one-year-old flounder that was 145 millimeters in length. What is the z-score for this length? Round the answers to at least two decimal places.
(b) Luis caught a two-year-old flounder that was 195 millimeters in length. What is the z-score for this length? Round the answers to at least two decimal places.
(c) Joe caught a one-year-old flounder whose length had a z-score of 1.3. How long was this fish? Round the answer to at least one decimal place.
(d) Terry caught a two-year-old flounder whose length had a z-score of −0.6. How long was this fish? Round the answer to at least one decimal place.
Solution :
Given that ,
mean = = 133 ( one year)
standard deviation = = 20
mean = = 156 ( two year)
standard deviation = = 24
a) x = 145
Using z-score formula,
z = x - /
z = 145 - 133 / 20
z = 0.60
b) x = 195
Using z-score formula,
z = x - /
z = 195 - 156 / 24
z = 1.63
c) Using z-score formula,
z = 1.3
x = z * +
x = 1.3 * 20 + 133
x = 159
d) Using z-score formula,
z = -0.6
x = z * +
x = -0.6 * 24 + 156
x = 141.6