Question

For each of the following analogical arguments, consider whether the listed adjustments to the argument would strengthen, weaken, or result in no change to the strength of the original argument.

Organic spinach from California was contaminated with E. coli bacteria. Thus, organic lettuce could also be contaminated with E. coli bacteria.

a. Suppose the lettuce was from California.

b. Suppose the lettuce was not organic.

c. Suppose that chard and arugula were also contaminated with E. coli bacteria.

d. Suppose it was broccoli, not lettuce, that had been contaminated with E. coli bacteria.

The new sports car Bob recently bought is equipped with a powerful V-8 engine, four-speed transmission, and racing clutch. The previous sports car Bob owned also had a V-8 engine, four-speed transmission, and racing clutch. So the new car is similar to the old one. Because Bob got several speeding tickets with his old car, he’s probably going to get speeding tickets with the new one.

a. Suppose Bob has owned six other sports cars and he has gotten a speeding ticket driving each of them.

b. Suppose Bob’s old car was turbocharged and so is his new one.

c. Suppose Bob’s new car has a four-cylinder engine.

d. Suppose Bob’s old car was black and his new one is red.

The stocks that Harold purchased are from Internet startups, are highly rated, and are selling for a low price. The stocks that Ashley bought are also from Internet startups, are highly rated, and are selling for a low price. Thus, Harold’s stocks are similar to Ashley’s stocks. Since Ashley’s stocks made a 10% profit in the first year, Harold can expect his stocks to make at least a 10% profit, too.

a. Suppose Gregg also purchased stocks from Internet startups that were highly rated and selling for a low price and they also made a 10% profit in the first year.

b. Suppose Harold bought stocks that were low-rated.

c. Suppose Harold bought stocks that were from a traditional brick-and-mortar business.

d. Suppose Harold bought his stocks from a broker.

Answer 1

Organic spinach from California was contaminated with E. coli bacteria. Thus, organic lettuce could also be contaminated with E. coli bacteria.

a. Suppose the lettuce was from California.
Strengthen - As Lettuce was from California too, it might has also got infected.
b. Suppose the lettuce was not organic.
Strengthen - More chances if lettuce is not organic, might have been contaminated.
c. Suppose that chard and arugula were also contaminated with E. coli bacteria.
Stengthen - As others are also getting comtaminated.
d. Suppose it was broccoli, not lettuce, that had been contaminated with E. coli bacteria.
No change

The new sports car Bob recently bought is equipped with a powerful V-8 engine, four-speed transmission, and racing clutch. The previous sports car Bob owned also had a V-8 engine, four-speed transmission, and racing clutch. So the new car is similar to the old one. Because Bob got several speeding tickets with his old car, he’s probably going to get speeding tickets with the new one.

a. Suppose Bob has owned six other sports cars and he has gotten a speeding ticket driving each of them.
Strengthen - As Bob has a record of getting speeding tickets for all cars
b. Suppose Bob’s old car was turbocharged and so is his new one.
Stengthen - As the new car is turbocharged too and more chances to get speeding tickets.
c. Suppose Bob’s new car has a four-cylinder engine.
No change - It does not matter
d. Suppose Bob’s old car was black and his new one is red.
No change

The stocks that Harold purchased are from Internet startups, are highly rated, and are selling for a low price. The stocks that Ashley bought are also from Internet startups, are highly rated, and are selling for a low price. Thus, Harold’s stocks are similar to Ashley’s stocks. Since Ashley’s stocks made a 10% profit in the first year, Harold can expect his stocks to make at least a 10% profit, too.

a. Suppose Gregg also purchased stocks from Internet startups that were highly rated and selling for a low price and they also made a 10% profit in the first year.
Stengthen - It means that the low prices, highly rated stocks are making 10% profit, it strengthens the argument.

b. Suppose Harold bought stocks that were low-rated.
Weaken - If stocks are low-rated, it would weaken the profit argument.
c. Suppose Harold bought stocks that were from a traditional brick-and-mortar business.
Weaken - The stocks might have a less chance to get 10% profit
d. Suppose Harold bought his stocks from a broker.
Weaken - Broker will get a cut of the profit, and Harold might not make 10% profit