Cool Down: How Bad Is It, Doc -
Doctors suspect a strain of bacteria found in the hospital is becoming resistant to
antibiotics. They put various concentrations of antibiotic in petri dishes and add some of
the bacteria to allow it to grow. The bacteria grow into groups in the dish called colonies.
After some time, the doctors return to the petri dishes and count the number of colonies
for the different amounts of antibiotic.
The data is plotted with a best fit line. The correlation coefficient was r = -0.83.
1. What does the sign of the correlation coefficient tell you about the relationship
between the number of bacteria colonies and the concentration of antibiotic in the
dish?
That its a strong negative
2. What does the numerical value of the correlation coefficient tell you about the
relationship between the number of bacteria colonies and the concentration of
antibiotic in the dish?
3. In a follow-up study, a group of scientists collect data that was fit by a linear model
with a correlation coefficient of r = -0.94. Which study suggests a stronger
relationship between the number of bacteria colonies and the concentration of
antibiotic--the doctors' study or the scientists' study? Explain your reasoning.