Earth is estimated to be 4.54 billion years old, plus or minus about 50 million years. Scientists have scoured the Earth searching for the oldest rocks to radiometrically date.

13.7 billion years oldMeasurements made by NASA's WMAPWMAPThe Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA Explorer mission that launched June 2001 to make fundamental measurements of cosmology -- the study of the properties of our universe as a whole. WMAP has been stunningly successful, producing our new Standard Model of Cosmology.https://map.gsfc.nasa.govWilkinson Microwave Anisotropy Probe (WMAP) spacecraft have shown that the universe is 13.7 billion years old, plus or minus about 130,000 years.

Student's t-test

T-Score A large t-score, or t-value, indicates that the groups are different while a small t-score indicates that the groups are similar.

Understanding the T-Test A t-test compares the average values of two data sets and determines if they came from the same population.

Key Takeaways A t-test is an inferential statistic used to determine if there is a statistically significant difference between the means of two variables.The t-test is a test used for hypothesis testing in statistics.Calculating a t-test requires three fundamental data values including the difference between the mean values from each data set, the standard deviation of each group, and the number of data values.T-tests can be dependent or independent.

A t-test is a statistical test that compares the means of two samples. It is used in hypothesis testing, with a null hypothesis that the difference in group means is zero and an alternate hypothesis that the difference in group means is different from zero. What does a t-test measure?