Ingrid thinks that Lizzy has been acting strange lately and is worried about her. According to her phone messages, this time last year, they were texting on average 70 times a day, but since last month, they've only been texting 50 times a day... (with a SD of 10). To determine whether things have changed between the two friends, what statistical test should be used here?

1. Paired samples t test
2. Simple linear regression
3. Single sample t test
4. Independent samples t test
5. Z test
6. Pearson's r correlation
7. One-way ANOVA