On Monday, the store took in $10,700. Alright, that's one day, Monday. On Thursday, a second day, the store took in $764. On which day was the daily cash register more unusual, and why? So, again, when you have a prompt that asks for unusual, your automatic trigger should be, "I need to find the z-score." Except the thing is, we now have two different days, two different observations. So, what that means is we are going to need to find the z-score for both Monday and Thursday. When it comes to these types of problems where you have two observations, it means you've got to find the z-score for each. We need to find the z-score for Monday when we are using $10,700, subtracting that from the mean of $9,200, divided by the standard deviation of $400. You also need to find a z-score for Thursday, which had an observed value of $7,640, compared to the mean of $9,200, divided by $400. I'll give you guys a moment to practically type this into your calculator and find the z-scores. The answers are up on the board, but we're not done yet. We haven't answered the problem yet. Z-score is only a part of the process. It's the middle step of the process. What type of unusualness do we have with either one of these? Yeah, these are both considered definitely unusual. 3.75 is definitely beyond three standard deviations from the mean. -3.9 is definitely beyond three standard deviations. Both of these are considered definitely unusual because both are beyond three standard deviations from the mean. In this case, both days have unusual, definitely unusual receipts. So, as an employer, it's very interesting to know that both days are definitely unusual. That still doesn't answer the question of more unusual. To determine more unusual, you have an inherent sense that we need to still compare these two values. So, the question is, how do you compare these two values? Ultimately, when you are comparing to determine more unusual or even less unusual, what you're going to do is ignore the plus and minus signs. You're just going to focus on the value of that number. So, in this case, on Monday, the value was 3.75, and on Thursday, you're going to look at 3.9. We are going to then compare these two values, and whichever value, again ignoring the plus and minus sign, whichever value is greater, is going to represent the day that was more unusual. In this case, when ignoring the plus and minus signs, notice how Thursday has the greater value. Because of that, Thursday is even further beyond the mean, making it even more unusual. So, in this case, because Thursday has the greater value, that emphasizes the fact that Thursday's receipt is more unusual.