Visual communication of conditional probabilities

Christian StolteNew York Genome Center

BIOVIS DESIGN CONTEST

WINNER

Mammography What does it mean to get a positive result? “The probability of breast cancer is 1% for a woman who participates in routine screening. If a woman who participates in routine screening has breast cancer, the probability is 80% that she will have a positive test result. If a woman who participates in routine screening does not have breast cancer, the probability is 9.6% that she will have a positive test result.”

Target Question: “What is the probability that a woman who participates in routine screening and receives a positive result has breast cancer?”

Answer: 7.8%

25 x 40 = 1,000

1% = 10 Cancers in 1,000

80% accuracy = 2 in 10 false negatives

9.6% false positives = 96 in 1,000

Stacked bar chart shows ratio

Labels help

Better readable from left to right

Trisomy The role of false positives in rare events“It is estimated that trisomy 21 is present in 1 out of every 800 births in Canada. It is estimated that trisomy 18 is present in approximately in 1 out of every 6,000 births. It is estimated that trisomy 13 is present in approximately in 1 out of every 16,000 newborns. The Harmony Test has been shown to have detection rates of up to 99% and false positive rates as low as 0.1% for trisomy 21, 18, and 13.”

Target Question: “What are the probabilities of having a child affected with a trisomy 21, 18, or 13 given a positive test result, respectively?”

One

One

in 800One

in 6,000One

in 16,000One

in 6,000One

in 16,000One

THANK YOU!