Final answer:
To determine if more than 30 percent of teens use a certain app to share pictures, a hypothesis test can be conducted. A hypothesis test can also be used to determine if more men use smartphones than women. To test at the 5% level of significance, the researchers would compare the test statistic to the critical value.
Step-by-step explanation:
To determine if more than 30 percent of teens use a certain app to share pictures, the researchers would conduct a hypothesis test. They would set up a null hypothesis (H0) that states the proportion of teens using the app is equal to or less than 30%, and an alternative hypothesis (Ha) that states the proportion is greater than 30%. They would then calculate the test statistic and compare it to the critical value to make a decision.
The researchers would use a hypothesis test to determine if there is good evidence that more men use smartphones than women. They would set up a null hypothesis (H0) that states the proportion of men using smartphones is equal to the proportion of women using smartphones, and an alternative hypothesis (Ha) that states the proportion of men is greater than the proportion of women. They would then calculate the test statistic and compare it to the critical value to make a decision.
To test at the 5% level of significance, the researchers would compare the test statistic to the critical value from the t-distribution with the appropriate degrees of freedom. If the test statistic is greater than the critical value, they would reject the null hypothesis and conclude that there is evidence to support the alternative hypothesis, which indicates that more men use smartphones than women.