Comparing the Means of Two Groups
The recommended test for a situation in which you have 2 groups and the dependent variable is on an interval- or ratio-scale is the independent or two-sample t-test.
The data for this exercise come from the first experiment in Strohmetz, Rind, Fisher, and Lynn (2002), who tested whether waiters received more tips if they gave customers chocolates along with the bill, compared to if they did not give the customers a chocolate. You can access a data file that simulates their data by downloading the following Excel data file:
String to Numeric Type
Open that file from within Jamovi. Look at the spreadsheet. You will see that there are there are two variables in this data set: Condition and Tip_Percentage. Condition refers to whether the customers were given chocolate or not. Tip_Percentage was calculated by dividing the tip by the pre-tax bill and multiplying by 100, so that a Tip_Percentage of 17 corresponds to a 17% tip. The two variables are differen types. Condition is a categorical (nominal) variable. It should have the following symbol next to the variable name: 
. . If it does not, and this is unlikely, double click on the variable name and in the window that opens above, select "Nominal". Next to the tip_percentage variable, there shoiuld be a titled ruler, like 
. This variable is a continuous variable (either interval or ratio). If this symbol is not next to your variable, double click on the variable name and select "continuous". A t-test needs the dependent variable to be continuous variables.