This is hubbles constant from my source
74.2 ± 3.6 (km/s)/Mpc
What does the ± mean?
That means that the value of the Hubble constant lies somewhere in the range of 74.2 -3.6 and 74.2 + 3.6. Every measured quantity has errors due to method and instrumentation called the error bounds.
For example, when using a ruler we usually assume an error equal to 1/2 the smallest division mark. Let's say you use a standard meter stick for a measurement of 10cm. Your error bound would be specified by 10 +/- .05 cm
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