I have measured 'Attitude towards a product' using Likert scale and I have measured 'Purchase Intentions to buy the product' also using Likert scale. Now I have to check "if Attitude influences Purchase Intention". I have ranked the Likert scale and performed Speamans rank correlation. Are there any other tests that can be performed with to see if Attitude (Likert scale) influences Purchase Interntion (also on Likert scale). Thanks!