In early 2001, the economy was slowing down and companies were laying off workers. A Gallup poll asked a random sample of workers how long it would be before they had significant financial hardships if they lost their jobs and couldn’t find new ones. They also classified their income. The classifications are

More than $50,000

$30,000 to $50,000

$20,000 to $30,000

Less than $20,000

Can we infer that differences exist between the four groups?