Kissing Right Most people are right-handed, and even the right eye is dominant for most people. Developmental
biologists have suggested that late-stage human embryos tend to turn their heads to the right. In a study reported in
Nature (2003), German bio-psychologist Onur Güntürkün conjectured that this tendency to turn to the right
manifests itself in other ways as well, so he studied kissing couples to see which side they leaned their heads to while
kissing. He and his researchers observed kissing couples in public places such as airports, train stations, beaches,
and parks. They were careful not to include couples who were holding objects such as luggage that might have
affected which direction they turned. For each kissing couple observed, the researchers noted whether the couple
leaned their heads to the right or to the left. They observed 124 couples, ages 13 to 70 years.
x The observational units in this study are the couples.
x The variable recorded in this study is whether each couple leaned right or left while kissing. It is categorical
data.
We want to use Güntürkün’s data to first test the conjecture that kissing couples tend to lean their heads to the
right. Use the symbol ݌ to denote the proportion of all kissing couples in the countries where the data were
collected that lean their heads to the right.
x The symbol ݌ is a parameter because the true value (population proportion) is not known
x We do not know the exact value of ݌ based on the observed data. The parameter value is a fixed but
unknown quantity. Our statistic from our observed data is the best guess of the value for the parameter.
The appropriate null and alternative hypotheses, both in words and in terms of the parameter ݌, for testing the
conjecture that kissing couples tend to lean their heads to the right more often than by random chance, are
x Null: 50% of couples in the population lean their heads to the right while kissing
Alternative: More than 50% of couples in the population lean their heads to the right while kissing
x Null: ݌ = 0.50
x Alternative: ݌ < 0.50
Our Collected Data
Of the 124 couples observed, 80 leaned their heads to the right while kissing. ݌̂ ≈0.645.
Socrative Question #1: Conduct a simulation analysis (using the One Proportion applet) to assess the strength of
evidence that the sample data provide for Güntürkün’s conjecture that kissing couples tend to lean their heads to