If you spend a long time in very cold water with your skin exposed, you can freeze to death. A wetsuit, which covers the whole body, helps keep the body warm. Surfers who spend a lot of time in the water have a safety rule: "If you surf in cold water, then wear a wetsuit."

You are interested to see whether surfers ever break this safety rule.

The cards below represent surfers. Each card represents one surfer. One side of the card tells whether that person surfs in cold water, and the other side tells whether that person is wearing a wetsuit. Which of the following cards would you definitely need to turn over to see if any of these surfers have broken the rule:

"If you surf in cold water, then wear a wetsuit."

Do not turn over any more cards than are absolutely necessary.

In the circus, performers who swing on the trapeze are performing high above the ground, and it can be quite dangerous if they lose their grip and fall. Circuses have a safety rule: "If you do a trapeze act, then you must use a safety net." The safety net can break someone's fall and prevent broken bones.

You are interested to see whether circus performers ever break this safety rule.

The cards below represent four circus performers. Each card represents one performer. One side of the card tells whether that performer does a trapeze act and the other side tells whether that performer uses a safety net. Which of the following cards would you definitely need to turn over to see if any of these circus performers are breaking the rule:

"If you do a trapeze act, then you must use a safety net."

Do not turn over any more cards than are absolutely necessary.

If you spray mace in someone's face, it is extremely painful and blinds them temporarily. Some people use mace for self-defense. In some parts of New York City, police advise people: "If you walk on the street at night, then carry a can of mace"

You are interested to know whether people ever break this rule.

The cards below represent four people who live in New York City and what they did on different nights. Each card represents one person on a different night. One side of the card tells whether the person walked on the street at night and the other side tells whether the person carried a can of mace. Which of the following cards would you definitely need to turn over to see if any of these people have broken the rule:

"If you walk on the street at night, then carry a can of mace"

Do not turn over any more cards than are absolutely necessary.

San Francisco is very hilly, and sometimes cars start rolling after being parked. So the San Francisco Police have a safety rule: "If you park on a hill, then you must set the emergency brake."

Imagine that you are a parking cop and you are checking whether people ever break this rule.

The cards below represent four cars in San Francisco. Each card represents one car. One side of the card tells whether the car is parked on a hill and the other side tells whether the emergency brake is set. Which of the following cards would you definitely need to turn over to see if any of these cars violate the rule:

"If you park on a hill, then you must set the emergency brake."

Do not turn over any more cards than are absolutely necessary.

It's dangerous to ride a bike at night when you can't see well, and it's safer if you have a light on your bike, so the police have a safety rule, "If you ride a bike at night, then use a light."

You want to see whether people ever break this safety rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether that person rode a bike at night and the other side tells whether that person used a light .

Which of the following cards would you definitely need to turn over to see if any of these people have broken the safety rule:

"If you ride a bike at night,

then use a light."

Do not turn over any more cards than are absolutely necessary.

Betsy is college student who owns an old, run-down car, which she sometimes lets her friends borrow. However, the car isn't very safe, because it leaks brake fluid, and without brake fluid the brakes don't work very well. Betsy doesn't want her friends to get hurt in an accident, so she warns them: "If you borrow my car, then you must add brake fluid."

You would like to see whether any of Betsy's friends ever break this safety rule.

The cards below represent four of Betsy's friends. Each card represents one friend. One side of the card tells whether that friend borrowed Betsy's car, and the other side tells whether that person added brake fluid. Which of the following cards would you definitely need to turn over to see if any of these people broke the rule:

"If you borrow my car, then you must add brake fluid."

Do not turn over any more cards than are absolutely necessary.

Roller coasters make some people very sick to their stomachs. The Rosenbergs have brought their children to an amusement park, but they don't want their children to get sick. They advise their children to follow the rule: "If you go on the roller coaster, then take some Dramamine." Dramamine prevents people from getting sick to their stomachs.

You are interested in whether any of the Rosenberg's children have broken this rule.

The cards below represent four of the Rosenberg's children. Each card represents one child. One side of the card tells whether that child rode on the roller coaster, and the other side tells whether that child took Dramamine. Which of the following cards would you definitely need to turn over to see if any of these children broke the rule:

"If you go on the roller coaster, then take some Dramamine."

Do not turn over any more cards than are absolutely necessary.

Hiking trails are often very uneven and rocky, and your feet can get very sore from stepping on lots of small rocks. Hiking boots have very thick soles to protect the foot. Experts advise people: "If you go hiking on a rocky trail, then wear hiking boots."

You are interested in whether people ever break this rule.

The cards below represent four people who went hiking. Each card represents one person. One side of the card tells whether that person went hiking on a rocky trail, and the other side tells whether that person is wearing hiking boots. Which of the following cards would you definitely need to turn over to see if any of these people are breaking the rule:

"If you go hiking on a rocky trail, then wear hiking boots."

Do not turn over any more cards than are absolutely necessary.

It's dangerous to drive through the desert if you don't have enough water to drink. People can get dehydrated very quickly. It's a good idea to follow the safety rule, "If you drive through the desert, then bring a gallon of drinking water in your car."

You want to see whether people ever break this safety rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether that person is driving through the desert and the other side tells whether that person brought a gallon of drinking water in their car .

Which of the following cards would you definitely need to turn over to see if any of these people have broken the safety rule:

"If you drive through the desert,

then bring a gallon of drinking water in your car."

Do not turn over any more cards than are absolutely necessary.

Parents who own guns are told, "If you keep your guns in the house, then unload them."

You want to see whether people ever break this rule, so you checked what four households did.

The cards below represent four families who own guns. Each card represents one family; all these families own guns. One side of a card tells whether or not that family keeps their guns in the house, and the other side tells whether or not the guns have been unloaded. Which of the following cards would you definitely need to turn over to see if any of these families are breaking the rule:

"If you keep your guns in the house, then unload them."

Do not turn over any more cards than are absolutely necessary.

Rabies shots can prevent people who have been exposed to rabies from developing the disease. You can get rabies by being bitten by an animal that has it. Doctors tell people, "If you have been bitten by a strange dog, then get rabies shots."

Imagine that you are a nurse and you want to see whether people ever break this rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether or not that person has been bitten by a strange dog and the other side tells whether or not that person got rabies shots. Which of the following cards would you definitely need to turn over to see if any of these people have broken the rule:

"If you have been bitten by a strange dog, then get rabies shots."

Do not turn over any more cards than are absolutely necessary.

The California hills are full of poison oak. If the leaves of poison oak touch a person's bare skin, the person can get a terrible rash. Park rangers in California tell hikers, "If you go off the trail, wear long pants."

Imagine that you are a park ranger and you want to see whether people ever break this rule.

The cards below represent four hikers. Each card represents one hiker. One side of the card tells whether or not that person went off the trail and the other side tells whether or not that person wore long pants. Which of the following cards would you definitely need to turn over to see if any of these hikers have violated the rule:

"If you go off the trail, wear long pants."

Do not turn over any more cards than are absolutely necessary.

When camping in the wilderness, one possible danger is getting bitten by a poisonous snake. Park rangers advise people, "If you go camping in the wilderness, then take a snake bite kit with you."

You want to see whether people ever break this safety rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether the person is camping in the wilderness and the other side tells whether that person has a snake bite kit with them.

Which of the following cards would you definitely need to turn over to see if any of these people are breaking the safety rule:

"If you go camping in the wilderness,

then take a snake bite kit with you."

Do not turn over any more cards than are absolutely necessary.

In the Midwest, tornadoes happen fairly frequently, and they can be very dangerous if you're above ground. Midwesterners know to follow the safety rule, "If there's a tornado in your area, go down in the basement."

You want to see whether people ever break this rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether there is a tornado in that person's area and the other side tells whether that person is down in the basement.

Which of the following cards would you definitely need to turn over to see if any of these people are breaking the rule:

"If there's a tornado in your area, go down in the basement."

Do not turn over any more cards than are absolutely necessary.

If any electrical appliance falls in a tub of water while it's turned on, anyone who's in contact with the tub of water will be electrocuted. So it's a good idea to follow the safety rule: "If you have a radio in the bathroom, then put the radio far from the bathtub."

You want to see whether anyone ever breaks this safety rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether the person is listening to the radio while taking a bath and the other side tells whether that person put the radio far from the tub.

Which of the following cards would you definitely need to turn over to see if any of these people are breaking the safety rule:

"If you listen to the radio while taking a bath, then put the radio far from the bathtub."

Do not turn over any more cards than are absolutely necessary.

Nuclear power plants use radioactive material to produce electrical power. These radioactive materials give off high levels of radiation. Radiation is very harmful; it can cause disease, breakdown of the immune system and cancer. The few rooms that contain these materials have lead walls, so most of the rooms in the power plant are insulated from the radiation. A radiation suit is a big bulky suit that covers someone from head to toe, using lead to block the radiation. Nuclear power plants have a safety rule for their employees, "If you work with radioactive materials, then wear a radiation suit."

You want to see whether anyone ever breaks this safety rule.

The cards below represent four people working in a nuclear power plant. Each card represents one person. One side of the card tells whether that person works with radioactive materials and the other side tells whether that person is wearing a radiation suit.

Which of the following cards would you definitely need to turn over to see if any of these people are breaking the safety rule:

"If you work with radioactive materials, then wear a radiation suit."

Do not turn over any more cards than are absolutely necessary.

Biology labs often study diseases by studying the viruses that cause disease. Of course, anyone who gets the virus on their skin can get quite sick. Paragon, Inc. is a drug company that studies diseases. Some of their labs study viruses, others are just chemical labs where they invent new drugs. Paragon has a safety rule, "If you work in the lab with viruses, then wear rubber gloves."

You want to see whether anyone ever breaks this safety rule.

The cards below represent four people who work for Paragon. Each card represents one person. One side of the card tells whether that person works in the lab with viruses and the other side tells whether that person is wearing rubber gloves.

Which of the following cards would you definitely need to turn over to see if any of these people are breaking the safety rule:

"If you work in the lab with viruses, then wear rubber gloves."

Do not turn over any more cards than are absolutely necessary.

Young kids are very curious, and often try to investigate the world around them by putting things in their mouths and tasting them. Many kids have gotten sick from eating laundry detergent or drinking bleach. Most parents know, "If you have young kids in the house, put dangerous chemicals out of reach."

Imagine that you're visiting some of your friends, and that you want to check whether any of them have broken this safety rule:

The following cards represent friends. One side of the card tells whether or not they have young kids, and the other side tells whether or not they’ve put dangerous chemicals out of reach. Which of the following cards would you definitely need to turn over to see if any of these friends are breaking the rule:

"If you have young kids in the house, put dangerous chemicals out of reach."

Do not turn over any more cards than are absolutely necessary.

It's dangerous to get underneath a car if the car is up on a jack, because the car could fall on you. So books about how to work on your own car give a safety rule, "If your car is up on a jack, do not get underneath it."

You want to see whether people ever break this safety rule.

The cards below represent four people. Each card represents one person. One side of the card tells whether that person's car is up on a jack and the other side tells whether that person got underneath their car.

Which of the following cards would you definitely need to turn over to see if any of these people have broken the safety rule:

"If your car is up on a jack, do not get underneath it."

Do not turn over any more cards than are absolutely necessary.

You are an anthropologist studying a tribe on Maku Island. Occasionally the tribesmen travel through the rainforest which is on the other side of the river from their village. The rainforest is a dangerous place because it is infested with poisonous snakes. In the past, tribesmen have died after being bitten by snakes when they were out hunting. However, the tribesmen found a solution to this problem. Smearing a special red clay on one's ankles causes people to give off an odor that repels snakes and makes them stay away from that person.

No person who has used this special red clay has ever been bitten by a snake, so the tribal elders have made the following rule: "If one goes into the rainforest, then one must first put red clay on one's ankles."

You are interested in whether the tribesmen ever violate this safety rule, so one afternoon you watched what some of the people in this tribe did.

The cards below represent four people whom you watched that day. Each card represents one person. One side of a card tells whether or not the person went into the rainforest that day, and the other side tells whether or not that person smeared red clay on their ankles. Which of the following cards would you definitely need to turn over to see if any of these people have broken the rule:

"If one goes into the rainforest, then one must first put red clay on one's ankles."

Do not turn over any more cards than are absolutely necessary.