Are twin births becomming more common? Part II Review Exercise R2.5 looked at the number of twin births by year from 1980 to 2014. Now we can include some inference:

a) State and test the standard null hypothesis for the slope. An Internet blogger claims that the increase in twin births can be explained by the increase in CO₂ levels in the atmosphere. He posts this regression for the same time period:

b) Do you think the growth in twin births is due to the amount of CO₂ in the atmosphere? Explain your reasoning.

Data From Exercise R2.5

In January 2012, the New York Times  published a story called Twin Births in the U.S., Like Never Before, in which they reported a 76 percent increase in the rate of twin births from 1980 to 2009. Here are the number of twin births each year (per 1000 live births). (www.cdc .gov/nchs/births.htm)

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TwinBirths/1000 Response variable is: R squared = 97.1% s = 0.9184 with 35 - 2 = 33 degrees of freedom Variable Intercept Year since 1980 Coefficient 18.2127 SE(Coeff) 0.3039 0.508261 0.0154 t-Ratio 59.9 33.1 P-Value <0.0001 <0.0001